The Countdown to Prevent Another Iranian Nuclear Crisis Just Began

Time is running out to avert a renewed nuclear crisis with Iran.

On August 28, Britain, France, and Germany (the E3) formally declared Iran in “significant non-performance” of its nuclear obligations under the Iran nuclear deal. As a result, within the next thirty days, all prior UN sanctions will be reimposed on Iran—known as the snapback mechanism—unless an agreement that satisfies all five veto-wielding Security Council members can be reached.

The E3’s timing is deliberate for two reasons. First is the approach of the so-called Termination Day on October 18, when the snapback mechanism and other key provisions of UN Security Council Resolution 2231, which endorsed the 2015 Joint Comprehensive Plan of Action (JCPOA), will expire. This extraordinary provision allows any JCPOA participant to unilaterally restore pre-2015 UN sanctions unless the Security Council affirmatively votes to block the move. Under the rules, the Security Council has thirty days to act, and if it fails to do so, all previous sanctions on Iran are reinstated. The second is Russia’s assumption of the Security Council presidency, which it could use to obstruct the process through the power of procedure, in October.

 The backdrop to this countdown is June’s unprecedented U.S. and Israeli strikes against Iranian nuclear facilities that escalated the long-running shadow war into direct confrontation. Iran retaliated by limiting inspections conducted by the International Atomic Energy Agency (IAEA). The E3 then began discussions with Tehran about a six-month extension of the snapback deadline, but Iran rebuffed them.

The risk is stark: If the snapback is approved, Iran could retaliate by withdrawing from the Nuclear Non-Proliferation Treaty (NPT) or halting cooperation with the IAEA—steps that would escalate the crisis and raise the risk of military confrontation. On the other hand, if the snapback provision expires on Termination Day without sanctions being reimposed, the Security Council will lose its last viable mechanism to penalize Iran for nuclear violations. In theory, sanctions could be reintroduced later, but only with unanimity among permanent members—an effective impossibility given Moscow’s and Beijing’s alignment with Tehran.

The United States should seize the initiative and press both its European allies and Iran to extend the snapback mechanism. To make this path viable, Iran would need to restore IAEA access to verify its stockpile of highly enriched uranium, while the United States and its partners would need to provide credible assurances—most importantly, a temporary prohibition on military action contingent on Iran’s compliance. Doing so would not simply be about preserving leverage—it would help prevent a spiral of escalation, maintain the possibility of renewed diplomacy, and protect the credibility of the nonproliferation regime.

Snapback

Snapback itself emerged as a unique innovation of the JCPOA, as a way to automatically bring back old UN sanctions if Iran was found to be violating its commitments. The word itself never appears in Resolution 2231, but the idea was simple: Sanctions relief would expire unless the Security Council voted to keep it in place.

Unlike standard Security Council practice, where any resolution requires consensus among the P5 members, the mechanism reversed the burden: Sanctions relief would expire automatically after thirty days unless the Security Council voted affirmatively to continue it. Because such a resolution could be vetoed by Britain, France, or the United States, neither Russia nor China could block the reimposition of sanctions.

Now that the E3 have formally launched the snapback process, the steps are straightforward. Within ten days, the Security Council must consider a resolution to preserve sanctions relief and vote in thirty days. If the resolution fails—because of a UK or French veto—the pre-JCPOA sanctions on Iran return. This would reimpose restrictions that had already expired, including the UN arms embargo and the ban on missile and drone transfers. 

E3 Position

The E3’s current position, which has significantly hardened over the years, is that any extension of the snapback mechanism cannot be unconditional. As an alternative, the E3 have reportedly floated a bridging arrangement: The snapback mechanism would be extended for six months but not triggered, conditional on Iran resuming negotiations with the United States, restoring full IAEA access to its facilities, and accounting for approximately 400 kilograms of highly enriched uranium, much of which almost certainly survived airstrikes.

In their August letter to the UN, the E3 stressed the goal was to buy time for negotiations while preserving the option of snapback if Iran remained noncompliant. At the same time, however, European officials publicly signaled their patience was running out and warned that, absent progress by the end of the month, they were prepared to trigger the snapback process.

Iran and Its Backers

Iran has pushed back with equal force. It has argued that the E3 is in breach of the JCPOA for failing to deliver the economic benefits promised under the agreement, once the United States withdrew in 2018. In a letter to the UN in July, Foreign Minister Abbas Araghchi accused the Europeans of effectively relinquishing their role as participants in the JCPOA by supporting or acquiescing to U.S. and Israeli military actions. Any attempt to reinstate terminated Security Council resolutions would be “null and void,” he claimed. In an August interview, he further warned that if the E3 invoked snapback, “it will lose its role in Iran’s nuclear path, and we will respond accordingly.” One of the measures frequently alluded to by Iranian officials has been withdrawal from the NPT, effectively terminating the basis for oversight over Iran’s nuclear program.

Tehran’s threat to withdraw from the NPT may be a bluff, or at least one that carries less practical weight than it appears. Iran has already restricted IAEA access so severely since February 2021, and even more dramatically following the June 2025 conflict, that formal NPT withdrawal might not substantially change the on-the-ground reality. However, the political ramifications would be enormous. Iranian NPT withdrawal would likely collapse any remaining diplomatic processes and intensify calls throughout the West and Israel for military action to prevent Iran from developing nuclear weapons. Iranian leaders certainly understand these risks, yet their willingness to brandish this threat reveals how high the stakes have become.

Moscow and Beijing have reinforced this argument. Russian diplomats contend that the E3 failed to follow the JCPOA’s dispute resolution steps in good faith, invalidating their claim to trigger snapback. Despite its efforts to delegitimize snapback, Russia also introduced a counter-resolution extending the snapback provisions—but without requiring Tehran to meet the E3’s conditions. With Chinese backing, the counter-resolution appears to be an effort by Russia to cast itself as a constructive actor while ensuring the blame for any escalation falls squarely on Europe. If the E3 refuse such a resolution—as they almost certainly will—Moscow can argue that it sought compromise but Europe forced confrontation. 

For Iran, the significance of snapback is more political than economic. Most trade with Iran is already blocked by U.S. sanctions, and either Russia or China is unlikely to comply. Symbolically and legally, however, UN sanctions would indicate that Tehran’s nuclear program is not just a bilateral issue with Washington but a threat of global concern. Snapback measures also bind all UN member states, creating a universal legal framework for isolating Iran. As former U.S. negotiator Richard Nephew observed, these restrictions force even Russia and China to “have a harder time convincing other states to break them.”

U.S. Policy

Since the June war, Washington has appeared increasingly disengaged, letting the Europeans take the lead while focusing on containment. But the United States should not remain passive, since current dynamics are likely to leave it strategically worse off.

By triggering snapback, there is a risk of Iranian retaliation that could spiral beyond control. Conversely, had the E3 allowed the snapback mechanism to lapse, it would have left Russia and China free to block any future sanctions while gradually normalizing Iran’s nuclear advances.

An alternative path—extending snapback—serves U.S. interests in three ways: It maintains multilateral leverage at the UNSC, it reduces the risk of Iranian withdrawal from the NPT, and it stabilizes the nuclear file long enough to create a narrow space for diplomacy. Whereas the E3 have tied a six-month extension to restoring full IAEA access and accounting for its highly enriched uranium stockpile, this proposal instead centers on graduated enrichment ceilings that phase down enrichment levels in exchange for security guarantees.

During the thirty-day window ahead of the vote, the United States should resume direct engagement with Iran. Even preliminary discussions could demonstrate to Tehran that Washington views the extension not as a trap but as an opportunity. To make the snapback extension credible, Iran would need to take meaningful steps with the IAEA, including allowing inspectors to regain access and eventually providing clarification on the unverified stockpile of highly enriched uranium. In turn, Washington could offer a conditional guarantee not to support or participate in further military strikes on Iranian nuclear facilities during the extension period, contingent on Iranian cooperation with the IAEA and compliance with the resolution. Such an assurance would signal that the extension is intended to stabilize the situation, not to buy time for more military action.

If Iran believes the United States is prepared to back negotiations under these conditions, it may be more willing to accept a prolongation of snapback. Europe alone cannot provide that guarantee—only Washington can. And if the United States steps forward to convince Iran of its intentions, Russia and China may be more likely to follow Iran’s lead and abstain on a resolution rather than veto it outright.

The U.S. administration should work closely with its European allies to present a unified extension proposal at the Security Council while actively shaping the draft of the resolution. The starting point should be a clear reaffirmation of IAEA oversight as the foundation for any limitations on Iran’s nuclear activities during the six-month extension. To avoid the current deadlock—where U.S. demands for zero enrichment risk triggering Russian or Chinese vetoes—the resolution should propose realistic, enforceable parameters.

One option—complementary to but distinct from the E3 position— would be to introduce graduated enrichment ceilings to guide the phased downblending of Iran’s existing stockpile of highly enriched uranium. For example, enrichment levels could be capped at roughly 60 percent in the first month, lowered to 20 percent by the third month, and returned to the JCPOA limit of 3.67 percent by the end of the sixth month. To appeal to Iran, the resolution could include language that explicitly prohibits military action, pursuant to Article 2(4) of the UN Charter, against Iranian nuclear facilities during the extension period, provided Iran meets verification benchmarks. This prohibition would be legally binding on all UN member states and would provide Iran with the security assurance necessary to accept meaningful transparency measures.

A snapback extension does not signal a U.S. retreat from its long-standing preference for zero enrichment. Rather, it reflects a recognition that insisting on maximalist demands in the current climate will foreclose diplomacy. A time-bound extension is not about conceding the principle, but about creating the political space to pursue it through negotiation. The snapback window could also be used to revive discussions on a regional fuel cycle consortium—an idea floated prior to the twelve-day war. Such a framework, anchored in international oversight, could offer Iran access to peaceful nuclear technology while addressing proliferation concerns and opening a broader conversation on regional nuclear constraints.

 Time Pressure

With military action offering significant risks of escalation, the United States should lead efforts to extend the snapback mechanism for six months.

Many in the United States and Israel will dismiss the prospects of diplomacy. However, military action offers only temporary solutions at enormous strategic cost. Israeli and American strikes can delay but not eliminate Iran’s nuclear capabilities, while virtually guaranteeing Iranian withdrawal from international oversight and acceleration toward weapons development in secret. The June strikes demonstrated this dynamic clearly: Rather than constraining Iran’s program, military pressure drove Tehran to further restrict IAEA access. Now, Washington has a little less than a month to forestall a coming storm.