Southeast Asian countries have a growing interest in having the five nuclear weapon states sign and ratify the protocol to the Southeast Asia Nuclear Weapon Free Zone Treaty in the near future. Making the protocol enter into force would help maintain the region of Southeast Asia as a zone of peace and neutrality at a time of increasing great power competition in the Asia-Pacific. The nuclear weapon states have so far resisted making progress due to four main concerns. However, changes in the global and regional strategic environment over the past few years offer new incentives for them to reconsider their positions. New development in military technologies also makes many of the original concerns less relevant today. If all parties, including the Southeast Asian countries and the nuclear weapon states, are willing to exercise political flexibility, there should be no serious obstacle for them to take the final step and close the deal soon. As the nuclear weapon states face increasing international pressure to make new progress on disarmament, signing and ratifying the protocol should be a top priority to consider.

1. When the five nuclear weapon states (NWS) met in Washington, DC in the fall of 2016 as part of the P5 (the five permanent members of the UN Security Council who happen to also be the five NWS: China, France, Russia, the United Kingdom, and the United States) process to discuss nuclear arms control and non-proliferation issues, they reaffirmed “their readiness to sign the protocol to the Southeast Asia Nuclear Weapon Free Zone [SEANWFZ] at the soonest possible time.” In 2017, the SEANWFZ Treaty will see its 20th anniversary of entering into force, but the protocol has not been signed by any of the NWS. Five years have passed since the last time the NWS came close to signing the protocol in 2012. New developments in the region and across the globe in recent years have important implications for the prospects of the protocol entering into force but have been largely neglected. This paper seeks to offer an assessment of existing disagreements and new developments with a view toward identifying possible areas of progress.

Main Concerns of NWS Countries

2. Based on open sources, the five countries designated as NWS under the Nuclear Non-Proliferation Treaty (NPT) have four main concerns about signing and ratifying the Protocol to the Southeast Asia Nuclear Weapon Free Zone Treaty.

Tong Zhao
Tong Zhao is a senior fellow in Carnegie’s Nuclear Policy Program based at the Carnegie–Tsinghua Center for Global Policy.
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3. First, some NWS do not want to offer a comprehensive negative security assurance to everyone within the zone. There are two issues about negative security assurance here. One is that some NWS such as the United States want to reserve the right to use nuclear weapons against non-NWS that are not members of the NPT or are not in good standing with their nuclear non-proliferation obligations. A few years ago, the United States had some concerns about the non-proliferation record of some ASEAN (Association of Southeast Asian Nations) countries such as Myanmar and was reluctant to issue a sweeping negative security assurance.

4. The second issue is not about ASEAN countries but about nuclear-armed countries. Article 2 of the protocol mandates that each state party undertakes not only not to use or threaten to use nuclear weapons against any state party to SEANWFZ, but also “not to use or threaten to use nuclear weapons within the Southeast Asia Nuclear Weapon Free Zone.”1 According to the treaty, the scope of the zone is defined as covering the territories of all ASEAN countries, as well as “their respective continental shelves and Exclusive Economic Zones (EEZ).” This means if some non-ASEAN nuclear-armed country deploys some nuclear weapons within the zone, for instance by deploying a nuclear ballistic missile submarine (SSBN) somewhere in an ASEAN country’s EEZ, the NWS will not be allowed to use or threaten to use nuclear weapons against this SSBN. Such a non-ASEAN country could be Russia, China, India, or North Korea, to whom the United States does not have a policy of offering negative security assurance and does not want to make such a commitment in the future.

5. Therefore, by signing the protocol all NWS countries will be essentially offering negative security assurances to one another and even to those de facto nuclear-armed countries outside of the NPT framework. There might even be concern that some nuclear-armed countries might therefore deliberately hide their SSBNs within the vast maritime area of the zone and use it as a sanctuary to protect their nuclear forces from being threatened. As a result, some NWS countries do not want their signature on the protocol to restrict their military options against other nuclear-armed countries.

6. Second, the treaty may pose a problem for the NWS’ free movement of nuclear-armed vessels within the zone. For the movement of nuclear-armed vessels (such as SSBNs and nuclear-armed surface ships), it is necessary to distinguish territorial water from EEZs. For movement within territorial waters, Article 7 of the treaty stipulates: “Each State Party, on being notified, may decide for itself whether to allow visits by foreign ships and aircraft to its ports and airfields, transit of its airspace by foreign aircraft, and navigation by foreign ships through its territorial sea or archipelagic waters and overflight of foreign aircraft above those waters in a manner not governed by the rights of innocent passage, archipelagic sea lanes passage or transit passage.” This stipulation distinguishes two situations: one is that “governed by the rights of innocent passage, archipelagic sea lanes passage or transit passage”; the rest constitutes the other situation.

7. For the first situation, the definition of “innocent passage” according to the United Nations Convention on the Law of the Sea (UNCLOS) does not really prohibit a foreign country’s SSBN from travelling through the coastal country’s territorial water, as long as the SSBN does not “exercise or practice with weapons,” “launch, land or take on board of any military device,” or conduct any other activities that are “prejudicial to the peace, good order or security of the coastal state.”2 For the second situation—that is, transit activities not governed by the rights of innocent passage, archipelagic sea lanes passage or transit passage—all NWS are expected to notify the coastal country and obtain approval before having their SSBNs travel within its territorial water or flying nuclear-armed aircraft in its airspace. This is interpreted by some NWS countries as undermining their capabilities to operate SSBNs and/or nuclear-armed aircraft. In the case of making port calls, if a vessel of a NWS country is going to make a port call at a coastal country, it is expected to declare whether it carries nuclear weapons. However, some NWS such as the United States usually do not make such explicit declarations and have deliberately embraced a policy of ambiguity. They see such stipulations as politically inconvenient and potentially troublesome.

8. For the movement of nuclear-armed vessels within a coastal country’s EEZ, the treaty and the protocol do not really impose substantive limitations. Despite often-heard claims to the contrary, no stipulation of either the treaty or the protocol explicitly limits the movement of nuclear-armed vessels and/or aircraft within the EEZ.

9. Third, the protocol may undermine the NWS capability to launch nuclear weapons from within the zone. It is clear that the NWS have no interest in using or threatening to use nuclear weapons against the ASEAN countries within the zone, although they seem to have reservations about committing to no use of nuclear weapons against any military assets of any nuclear-armed countries within the zone, as explained in the first point. That said, given that the geographical scope of the zone is defined broadly in the treaty as covering not only territorial waters but also EEZs, the zone constitutes a very significant part of the region’s maritime area which extends from the eastern part of the Indian Ocean to the western part of the Pacific. Furthermore, this region occupies a strategically important location that connects Asia with Oceania and links the Indian Ocean with the Pacific.

10. The SSBNs of some NWS countries may transit through and operate within the EEZs of some ASEAN countries from time to time, and may want to reserve the right to launch their SLBMs (submarine launched ballistic missiles) from these waters against a target outside of the zone in case there is a need to do so. However, Article 2 of the protocol stipulates that the NWS “undertake not to use or threaten to use nuclear weapons within the Southeast Asia Nuclear-Weapon-Free Zone.” This could remove the NWS right to launch nuclear missiles from within the zone against any targets including those outside the zone. This is seen by some NWS as potentially undermining their nuclear deterrence capabilities.

11. Fourth, the exact geographical boundaries of the zone are unclear and may have implications for territorial sovereignty. Four ASEAN countries—the Philippines, Vietnam, Malaysia, and Brunei—have unresolved maritime territorial disputes with mainland China and Taiwan in the South China Sea. A fifth ASEAN country—Indonesia—does not claim sovereignty over any land features within South China Sea, but its claimed EEZ overlaps with the claims of some of the above-mentioned countries. Given the unresolved maritime disputes, the exact geographical boundaries of the zone are unclear. This can create potential problems for dispute resolution regarding compliance with the treaty and the protocol’s provisions. In addition, China may worry that its signature on the protocol may be interpreted as a tacit recognition of the sovereignty claims made by other ASEAN countries in South China Sea and therefore potentially undermine its own legal and political standing in the unresolved disputes.

Evolving Strategic Environment

12. A few years have passed since the last time the NWS came close to signing the protocol in 2012. Some new developments in the general strategic environment may have brought about important changes in the NWS and ASEAN countries’ strategic calculations about SEANWFZ.

13. The prospect of an international treaty to ban nuclear weapons introduces new pressure for the NWS to sign the protocol sooner rather than later. On October 27, 2016, the First Committee of the UN General Assembly adopted resolution L.41 to launch negotiations in 2017 on a treaty to outlaw nuclear weapons. A vast majority of the UN member states—123 countries—voted in favour of the resolution, which was then officially approved by the General Assembly on December 23. As the negotiations are scheduled for March and June–July 2017, the NWS will face unprecedented pressure.

14. While the majority of non-NWS have become increasingly serious about pursuing this “radical” approach of promoting nuclear disarmament, the NWS have an ever greater need to demonstrate that their preferred approach—the “incremental” approach of achieving nuclear disarmament through a gradualist step-by-step process—can actually work. Signing the protocol and thus making Southeast Asia a nuclear-weapon-free zone to the fullest extent will constitute a significant achievement of the incremental approach.

15. Furthermore, if the negotiations in 2017 successfully result in an international treaty to prohibit nuclear weapons, it would be much harder for the NWS and ASEAN countries to bridge their remaining differences by then. An important purpose of this treaty, if successfully negotiated, would be to delegitimize and stigmatize nuclear weapons, by proclaiming them to be illegal. This would not change the fact that NWS will continue possessing and operating their nuclear weapons, but it would make it harder for ASEAN countries to want to appear to allow the transit of nuclear-armed vessels/aircraft through their territorial waters and EEZs. If the NWS are concerned about the potential restriction of the treaty and the protocol on the movement of their nuclear-armed vessels/aircraft within the zone now, the restriction is only going to increase over time as nuclear weapons are outlawed and stigmatized internationally. Under such circumstances, ASEAN countries would be less likely to compromise on reducing the restriction. It is better for the NWS to close the deal now than to wait longer.

16. On the part of ASEAN countries, they also have a renewed interest in having the NWS sign and ratify the protocol sooner rather than later. One of the original objectives of the ASEAN countries in setting up SEANWFZ in the first place was to make Southeast Asia a zone of peace, freedom and neutrality, not to be affected by great power competition.3 In recent years, however, the risk of great power competition affecting the peace, stability and neutrality of Southeast Asia has significantly increased. Growing tensions between China and some ASEAN countries over maritime sovereignty disputes in the South China Sea, coupled with the rebalance to Asia strategy of the United States, have threatened to undermine internal cohesion among ASEAN countries. The risk of ASEAN countries being forced to choose sides in a rising strategic rivalry between Washington and Beijing has grown considerably. With President Donald Trump appearing poised to heighten the strategic competition with China across the board, the risk of ASEAN countries being dragged into a serious great power competition is ever increasing.

17. Although China’s relations with the Philippines and Vietnam have improved since the second half of 2016, the United States has maintained frequent and significant military presence in the South China Sea, including periodic freedom of navigation operations, military surveillance and reconnaissance activities, and the dispatch of large warships, including aircraft carriers, to the South China Sea. China has also stepped up the deployment of countermeasures, including installing more defence assets on selected islands and holding military exercises. With China’s reported deployment of SSBNs in South China Sea, the cat-and-mouse game between China’s pro-SSBN forces and America and its allies’ anti-submarine-warfare forces will become more intense over time. The risk of conventional military confrontation, along with the potential for quick escalation, will grow.

18. To save themselves from this increasing risk, ASEAN countries should have a greater and more urgent interest in staying away from any great power competition in the future. Having the NWS sign and ratify the protocol and thus make Southeast Asia a complete nuclear-weapon-free zone will contribute to this endeavour.

19. On the other hand, through the international campaign on the humanitarian consequences of nuclear weapons and the UN mandate to negotiate a nuclear ban treaty, the majority of non-NWS in the world continue to impose more pressure against NWS and make them more isolated now than ever on nuclear disarmament. With the need to huddle each other for warmth and comfort, members of the NWS will be less willing to break ranks with the whole group and be the first to sign the protocol. This means the ASEAN countries and the international community in general need to engage with all five NWS simultaneously, and need to do so proactively. The objective would be to avoid making the NWS feel further alienated, which would only make them retreat further back into their corner of comfort and refuse meaningful cooperation.

Changing Technologies

20. Developments in strategic military technologies may affect the NWS incentives to sign the protocol. As discussed in the first section of this paper, the first concern of some NWS countries involves the possibility that some nuclear-armed countries might use the zone as a sanctuary for strategic military assets such as SSBNs. However, with the development of new technologies, the need to use nuclear weapons to threaten another nuclear-armed country’s military assets in the zone has greatly reduced. For instance, for the purpose of countering another country’s SSBNs, no one nowadays still seriously contemplates using nuclear weapons. There are a wide range of conventional weapons that are readily available that can be used to effective counter enemy SSBNs. As long as an SSBN can be detected and tracked, it can be dealt with through conventional military means and there is no need to bring in nuclear weapons which can cause much greater collateral damage and environmental contamination, let alone the political and diplomatic repercussions which come along with using nuclear weapons.

21. The third concern of some NWS is that the protocol may undermine their capabilities to launch nuclear weapons (for example from SSBNs) from within the zone against targets outside of the zone. Over the past decades, many NWS have greatly reduced the role of sea-based tactical nuclear weapons. As a result, the general need to launch nuclear weapons from within the zone has also decreased. In the case of the United States, nuclear-armed sea-based cruise missiles have been retired; and nuclear weapons have long been removed from all surface ships. Nowadays, the navies of the United States and many others rely on advanced conventional weapons such as conventional cruise missiles which can be launched by submarines and/or surface ships.

22. That said, nuclear-armed SLBMs still play a very important role in the national security strategies of the NWS. Besides being a very survivable and thus essential instrument for second strike, some argue that SLBMs can be used as very effective first strike capabilities. Some U.S. scholars, for instance, argue that the accuracy of current American SLBMs is much higher than before; and by setting the optimal air burst altitude for the nuclear warheads, SLBMs can become a very lethal first strike weapon against small nuclear-armed countries without generating huge collateral civilian damage or massive radioactive fallout.4 Nonetheless, given the high survivability and mobility of U.S., Russian, British, and French SSBNs, as well as the locations of their potential targets, there is no obvious reason why they have to launch SLBMs from within the zone. In other words, by committing not to launch SLBMs from within the zone, their nuclear deterrent would not be affected in any meaningful manner.

23. The only exception might be China. As opposed to the other NWS, the South China Sea is a much more important operation area for China’s young SSBN fleet. The current Chinese SSBN in service—the 094 class—is still relatively noisy and may not be very survivable if patrolling in the Pacific Ocean. Therefore, China is more likely to deploy its SSBNs in South China Sea during peacetime where the hydrological environment is friendly and China’s general-purpose forces can provide protection.5 Therefore, in theory, China should be the strongest opponent among the NWS of the treaty and the protocol, given that it may undermine China’s capability to patrol its SSBNs and to launch SLBMs within the zone.

24. However, China in reality has been the most supportive of the protocol among the NWS and was willing to sign the protocol, as well as a memorandum of understanding with ASEAN on the protocol, in 2012. The signing was later postponed (and remains postponed to this day) because the other four NWS submitted reservations to the protocol and ASEAN wanted to postpone the signing until the matter of the reservations was completely resolved. It is possible that China does not see the treaty and the protocol as potentially undermining its SSBN operations in the South China Sea, for reasons the paper will address in the last section.

China’s Potential Interests

25. In contrast to potential concerns surrounding the technical limitation on its SSBN operations in South China Sea, China seems to have been worried most about the political implications of signing the protocol for its territorial claims in the region. Given the various and often overlapping sovereignty claims over the land features and associated EEZ claims, the geographical boundary of the zone is not clear. As mentioned above, China worries that its signature on the protocol might be read as a tacit recognition of the other’s territorial claims. Moreover, if the protocol enters into force, disputes during the implementation of the treaty and the protocol might exacerbate existing clashes over different sovereignty claims. Especially after the Hague Tribunal’s verdict in July 2016 ruled in favour of the Philippines over China, China’s South China policy has faced an unprecedented crisis.

26. However, to many observers’ surprise, the situation over the South China Sea has turned around quickly since late 2016. New leaders and policies embraced by the Philippines and Vietnam have helped to greatly mend ties with China. Bilateral relations have improved substantially and Beijing has shown great interest in using this opportunity to further de-escalate tensions with Manila and Hanoi and to improve its overall relationship with ASEAN. Signing the protocol soon can help reassure regional countries that China is sincerely moving towards shelving the territorial disputes. Doing this in the near term will be especially helpful for improving China’s image in the region and the world.

27. Better relations between China and ASEAN countries, especially other claimant countries, will also mean that the United States would have less incentive to intervene in the South China Sea dispute, which would also contribute to China’s security interests. In the long run, as more countries in Southeast Asia might consider developing their own nuclear energy programs in the future, China will have a growing interest in making sure that those nuclear energy programs will not be used as springboards to military nuclear capabilities. Signing the protocol and enhancing SEANWFZ is an important way to secure this long term interest.

Uncertain U.S. Policies

28. Among the NWS, the United States remains the most influential player regarding the future of the protocol. Some regional developments in recent years may help reduce U.S. concerns about the protocol. For instance, Myanmar’s domestic political reform and democratization may have helped reduce American concern about Myanmar’s intention to secretly seek nuclear weapons or other weapons of mass destruction. Increasing transparency about Myanmar’s military programs and improving U.S.–Myanmar relations may make the United States more comfortable about issuing across-the-board negative security assurances to all ASEAN countries.

29. In Northeast Asia, however, North Korea’s nuclear and missile capabilities continue to rapidly improve. The risk of onward proliferation by North Korea to illegally sell nuclear technologies and materials to foreign countries or even non-state actors may increase over time. Therefore, the United States should have more urgent interest in strengthening counter-proliferation regimes such as the Proliferation Security Initiative (PSI) which can make the shipping of prohibited items from and to North Korea more difficult. In Southeast Asia, all ASEAN countries except Indonesia, Laos, and Myanmar are PSI participants. If the United States would like to take the lead in signing and ratifying the protocol, it would have a better chance to persuade the three remaining ASEAN countries to join PSI.6

30. That said, although former President Barack Obama was personally committed to the cause of nuclear arms control and non-proliferation, President Donald Trump does not appear to care much. He has openly said “let it be an arms race” during a TV interview, and has also appeared open to the idea of allowing America’s East Asian allies to develop nuclear weapons to defend themselves. Moreover, with Trump’s expressed preference for keeping all options open and being unpredictable, it might be difficult for one to imagine that Trump will voluntarily give up some (albeit very small) existing right by signing the protocol. For all these reasons, the United States remains a critically important actor but also the biggest factor of uncertainty for the future of the protocol.

Conclusion: Necessary Compromises and Future Prospects

31. Looking to the future, ASEAN countries can also offer some necessary compromise to facilitate the signing of the protocol by the NWS. Existing obstacles are not unresolvable, especially if people are willing to consider flexible interpretation of some provisions.

32. Among the four main concerns of the NWS, the first one is becoming less of a concern over time. With Myanmar’s proliferation risk reducing, the United States should be more comfortable about providing negative security assurances to all ASEAN countries. Doing so will not contradict existing U.S. nuclear declaratory policy, because the 2010 U.S. Nuclear Posture Review Report already commits the United States to renouncing the use of nuclear weapons against NPT members in good standing with their nuclear non-proliferation obligations. If any ASEAN country breaks its non-proliferation commitment in the future, it would have already violated the SEANWFZ Treaty. In that case, the United States would be no longer bound by the protocol to provide negative security assurances to that country. Moreover, new technologies have also made it harder to hide proliferation activities and therefore should help reduce American concerns. In addition, technology development makes it much less necessary for NWS to use nuclear weapons against another nuclear-armed country’s military assets within the zone. As a result, the overall need to use nuclear weapons against anyone within the zone has greatly diminished.

33. The second concern about free movement of nuclear-armed vessels/aircraft within the zone is also resolvable. As discussed above, the treaty and the protocol do not really restrain the movement of nuclear-armed vessels/aircraft within ASEAN countries’ EEZs. Given that EEZs constitute a much larger maritime area than territorial waters, a major part of the problem already resolves itself. Within territorial waters, for the movement of nuclear-armed vessels/aircraft in manners not governed by the rights of innocent passage, the concern is that NWS may need to notify the coastal country and get approval. However, Article 7 of the treaty reads: “Each State Party, on being notified, may decide for itself whether to allow visits by foreign ships and aircraft.” There seems to be room to interpret the text as saying that: if a state party is notified, it may decide “whether to allow visits by foreign ships and aircraft.” In other words, the NWS are not explicitly required to make a notification. In which case, the coastal country would not have to make an explicit decision to agree or reject. This interpretation will keep the existing policy of ambiguity and essentially remove the concern of the NWS.

34. The third concern, about the launch of nuclear weapons from within the zone, can also potentially be addressed. Increasingly, NWS have much less of a need to use sea-based tactical nuclear weapons in general. Even with regard to the launch of nuclear SLBMs, the text of the protocol uses a very general term of “use.” Article 2 of the protocol states that the NWS “undertake[s] not to use or threaten to use nuclear weapons within the Southeast Asia Nuclear Weapon-Free Zone.” Given the ambiguity around the term “use,” NWS may be able to make an argument that the launch of nuclear SLBMs from within the zone against targets outside of the zone does not constitute “use” of nuclear weapons “within” the zone. With enough political will, a compromise can be made based on this flexible interpretation of the text.

35. The fourth and last concern about unclear boundaries and territorial disputes does not have to be a significant obstacle. All NWS recognize that the complex territorial disputes in South China Sea won’t be easily resolved and will probably remain in place for the near- to mid-term future. The only practical concern about the unclear boundaries of the zone is that if disputes take place they may be difficult to resolve because countries may have different interpretations about where the geographical boundaries are. However, if ASEAN and the NWS are going to implement flexible interpretations about the movement of nuclear-armed vessels/aircraft and the launch of SLBM from within the zone, they would have already removed the most likely dispute scenarios. Therefore, dispute resolution should not become a major problem.

36. Regarding the political implications of signing the protocol for existing territorial disputes, China has already shown a great degree of restraint and flexibility. When it came to preparing for signing the protocol in 2012, China seemed confident that it could minimize such concerns by signing a separate memorandum of understanding with ASEAN countries. As the tensions over South China Sea have reduced since late 2016, China is working harder to improve relations with other claimant countries as well as ASEAN as a whole. In its white paper on Asia-Pacific security cooperation released in January 2017, China claims that “China has solved all the remaining issues concerning the protocol with ASEAN, and looks forward to the signing of the protocol at an early date.”7 It is hopeful that China will not make this concern a deal breaker.

37. The evolving strategic environment in the region, combined with the ever-louder calls of non-NWS for progress on disarmament, will give important incentives for the NWS to deliver tangible results on their disarmament commitments. Technological development has also made some of the previous concerns about the protocol increasingly less relevant. Making the SEANWFZ protocol enter into force as soon as possible serves everyone’s interests. A collective effort by all stakeholders in the region can achieve historic breakthroughs, which can become important bedrock for regional stability at a time of increasing geopolitical uncertainty.

1 “Protocol to the Treaty on the Southeast Asia Nuclear Weapon-Free Zone,” Association of Southeast Asian Nations,

2 “United Nations Convention on the Law of the Sea (Unclos),” United Nations,

3 Hasjim Djalal, “Rethinking the Zone of Peace, Freedom and Neutrality (ZOPFAN) in the Post-Cold War Era,” (Centre for South East Asian Studies, Indonesia, 31 May 2011); Jozef Goldblat, “Nuclear-Weapon-Free Zones: A History and Assessment,” The Nonproliferation Review (Spring–Summer 1997).

4 “Workshop on Emerging Technologies and Strategic Stability,” (Charlottesville, Virginia, 2 December 2016).

5 Tong Zhao, “China’s Sea-Based Nuclear Deterrent,” in Ashley J. Tellis, ed., Regional Voices on the Challenges of Nuclear Deterrence Stability in Southern Asia (Washington DC: Carnegie Endowment for International Peace, 2016).

6 Catharin Dalpino, “Can Asean Sell Its Nuclear Free Zone to the Nuclear Club?,” (Washington DC: Policy Brief, Sigur Center for Asian Studies, George Washington University, October 2014).

7 “China’s Policies on Asia-Pacific Security Cooperation,” State Council Information Office,

This was originally published as an APLN and CNND policy brief.