Three factors produced the hopeful moment of Reykjavik. The United States and the Soviet Union recognized the reciprocal devastation they could impose on each other, and with the Soviet defeat in Afghanistan, both were tiring of global military adventures. The leaders of both countries morally understood that nuclear weapons blighted civilization and were problems to be gotten rid of rather than solutions to be brandished. And third, Ronald Reagan and Mikhail Gorbachev were change-minded leaders who applied their boldness to the goal of eliminating nuclear dangers.

None of these three factors operates today.

The United States now sees itself as the global hegemon. Its national security establishment seeks to project dominant military power in order to prevent a peer competitor or a coalition of powers from rising to balance US power. Leaders in Washington and, indeed, Moscow, Paris, Beijing, Tel Aviv, Islamabad, Pyongyang and perhaps other capitals see their nuclear arsenals more as valued assets than as problems to be eliminated, and they resist moral questioning of this position. And, with the exception of George Bush and Tony Blair in their campaign to disarm and liberate Iraq, leaders of nuclear powers have for years lacked strength, vision and boldness.

Reagan also displayed an optimism that is now largely absent from post-Iraq America and from other major powers. Perhaps a consummation of the Reykjavik proposal would have given birth to a more optimistic future, and the nuclear pessimism of our day would have become the dismal fantasy of airport bookstand novelists rather than the agate gloom of daily headlines. But great disparities in power and prestige, unregulated by universally enforced rules, motivate the disadvantaged to seek the magic balancing potential of nuclear weapons.

The vast majority of the world's states do not possess nuclear weapons and cannot match the military, economic and political power of the nine states that do (though two of the nine--North Korea and Pakistan--are hardly major powers). Yet without universal rules to govern the international system, even nuclear weapons states will find security difficult to obtain. A rule-based system cannot be sustained globally without the vast majority of states believing that voluntary adherence to international rules and obligations is mutually beneficial and that rules will be fairly enforced.

This leads back to the disarmament bargain on which the nonproliferation regime was founded in the Non-Proliferation Treaty in 1968. The states that did not then possess nuclear weapons agreed not to acquire such weapons, while the five that did--Britain, China, France, the Soviet Union and the United States--agreed in return to get rid of their nuclear arsenals at some undetermined time. The five pre-1967 nuclear weapons states plus Israel, India and Pakistan (which never signed the treaty) no longer fool anyone that they take disarmament seriously. The United States leads the pack in still refusing to ratify the Comprehensive Test Ban Treaty, which is the most basic benchmark of fidelity to the goal of nuclear abolition.

Instead of keeping bargains premised on international equity and universal standards, Washington prefers to eliminate bad governments and bend the rules for friendly ones. Iraq was invaded, Iran is vilified, North Korea eschewed for not complying with nonproliferation rules, but the Bush Administration did not hesitate to change those rules to accommodate India's nuclear arsenal and may do so with other friends in the future. Russia neither resists nor poses alternatives to US nonproliferation policy; it simply doesn't help much. Iran may get the bomb because Russia won't support Security Council diplomacy tough enough to pose real costs to the Iranian government, and the United States will not offer Iran a relationship that would change its calculation about its nuclear program. The mere prospect of an Iranian bomb in turn has prompted Egypt to announce a big civilian nuclear program; Turkey is making similar noises. North Korea's bomb, plus the rise of Chinese power and disillusion about the future of cooperative security, may lead Japan and South Korea to flirt with acquiring nuclear weapons. Brazil is going into the uranium enrichment business, which Argentina notes with interest.

None of these potential next-wave proliferators would pose a direct threat to the United States, but such proliferation would cause deep and wide-ranging international insecurity. The United States would have to step in to try to reorder the world and allay the insecurities that result from more proliferation. Yet most other countries would be reluctant to cooperate either in punishing or containing the proliferators or in improving nuclear technology rules. They would want to know what's in it for them.

If the United States, Russia and other countries with nuclear weapons were not offering some meaningful equity, the system of rules would give way to the unpredictability, cost and insecurity of nuclear anarchy. It is this prospect that should lead us to put nuclear disarmament back on the world's political agenda today.

Maybe disarmament is not the equity others will demand now, but until leaders with the attributes of Gorbachev and Reagan arise to begin international negotiations to replace the existing disarmament bargain, the risk of nuclear proliferation will grow. Nuclear threats cannot be diminished without the vision and political will that the Reykjavik leaders shared.

This article originally appeared as part of a forum called "Gone Nuclear: How the World Lost Its Way," from the October 23, 2006 web-only edition of The Nation magazine. To see the full exchange, please go to www.thenation.com