We should be aware, however, that a next step of deeper reductions will hardly be attainable unless there is agreement on extensive cooperation on missile defense. Russia is deeply suspicious that the missile shield could enable the United States to launch an attack on any target in Russia while itself remaining immune to any such attacks. Further bilateral disarmament will also be impeded if Russia feels that the NATO alliance seeks to encircle it by expanding its military cooperation through membership or otherwise with more states neighboring Russia.

The signing on Thursday will take place one year after President Obama’s presentation in Prague of a detailed program for the revival of global nuclear arms control and disarmament. Later this month he will be the host in Washington of a large summit meeting that will focus on nuclear security. In May, the operation of the Nuclear Non-Proliferation Treaty will be the subject of review at a conference in New York in which nearly all governments in the world will take part. The review that took place in 2005 ended in acrimony and some predicted the end of the treaty.

Through adherence to the nonproliferation treaty that was concluded in 1970, states have committed themselves to stay away from nuclear weapons or to move away from these weapons. If all states had joined and fulfilled their commitments, the treaty would have led by now to a world free of nuclear weapons. This has not happened, of course. The number of nuclear weapons, which peaked at more than 50,000 during the Cold War, is still over 20,000 — most of them in the United States and Russia. The number of states with nuclear weapons has gone from five to nine since 1970.

There is also frustration at the lack of progress on many important items relevant to the treaty. The Comprehensive Test Ban Treaty has not entered into force because the United States, China and a number of other states have not ratified it. The negotiation of a convention prohibiting the production of enriched uranium and plutonium for weapons remains blocked at the Geneva Disarmament Conference. The Additional Protocol of the International Atomic Energy Agency for strengthened safeguards inspections remains unratified by a large number of states, including Iran.

Some items are bound to attract much attention at the nonproliferation treaty review conference in May. One is that 20 years after the end of the Cold War, the obligation of five nuclear-weapon states under the treaty to negotiate toward nuclear disarmament has not led us anywhere near zero. Another grievance — especially among Arab states — is that Israel has nuclear weapons and has refrained from adhering to the treaty. A third is that the treaty has been violated by several states. Although Iraq and Libya have been brought into compliance, North Korea has not and Iran and perhaps others might be aiming to ignore the treaty.