With the release of the 2010 Nuclear Posture Review, the signing of the new START Treaty and President Obama's Nuclear Security Summit, it's been a memorable time for CISAC's security experts, many of whom played prominent as well as behind-the-scenes roles in negotiations related to these events, as ongoing news coverage reveals.

THIS has been a remarkable time for the Obama administration. After a year of intense internal debate, it issued a new nuclear strategy. And after a year of intense negotiations with the Russians, President Obama signed the New Start treaty with President Dmitri Medvedev in Prague. On Monday, the president will host the leaders of more than 40 nations in a nuclear security summit meeting whose goal is to find ways of gaining control of the loose fissile material around the globe.

New Start is the first tangible product of the administration's promise to "press the reset button" on United States-Russian relations. The new treaty is welcome. But as a disarmament measure, it is a modest step, entailing a reduction of only 30 percent from the former limit - and some of that reduction is accomplished by the way the warheads are counted, not by their destruction. Perhaps the treaty's greatest accomplishment is that the negotiations leading up to its signing re-engaged Americans and Russians in a serious discussion of how to reduce nuclear dangers.

So what should come next? We look forward to a follow-on treaty that builds on the success of the previous Start treaties and leads to significantly greater arms reductions - including reductions in tactical nuclear weapons and reductions that require weapons be dismantled and not simply put in reserve.

But our discussions with Russian colleagues, including senior government officials, suggest that such a next step would be very difficult for them. Part of the reason for their reluctance to accept further reductions is that Russia considers itself to be encircled by hostile forces in Europe and in Asia. Another part results from the significant asymmetry between United States and Russian conventional military forces. For these reasons, we believe that the next round of negotiations with Russia should not focus solely on nuclear disarmament issues. These talks should encompass missile defense, Russia's relations with NATO, the Conventional Armed Forces in Europe Treaty, the Intermediate-Range Nuclear Forces Treaty, North Korea, Iran and Asian security issues.

Let's begin with missile defense. Future arms talks should make a serious exploration of a joint United States-Russia program that would provide a bulwark against Iranian missiles. We should also consider situating parts of the joint system in Russia, which in many ways offers an ideal strategic location for these defenses. Such an effort would not only improve our security, it would also further cooperation in dealing with the Iranian nuclear threat, including the imposition of consequential sanctions when appropriate.

NATO is a similarly complicated issue. After the cold war ended, Russia was invited to NATO meetings with the idea that the country would eventually become an integral part of European security discussions. The idea was good, but the execution failed. NATO has acted as if Russia's role is that of an observer with no say in decisions; Russia has acted as if it should have veto power.

Neither outlook is viable. But if NATO moves from consensus decisions to super-majority decisions in its governing structure, as has been considered, it would be possible to include Russia's vote as an effective way of resolving European security issues of common interest.

The Russians are also eager to revisit the two landmark cold war treaties. The Conventional Armed Forces in Europe Treaty enabled NATO and Warsaw Pact nations to make significant reductions in conventional armaments and to limit conventional deployments. Today, there is still a need for limiting conventional arms, but the features of that treaty pertaining to the old Warsaw Pact are clearly outdated. Making those provisions relevant to today's world should be a goal of new talks

Similarly, the 1987 treaty that eliminated American and Soviet intermediate-range ballistic missiles was a crucially important pact that helped to defuse cold war tensions. But today Russia has neighbors that have such missiles directed at its borders; for understandable reasons, it wants to renegotiate aspects of this treaty.

Future arms reductions with Russia are eminently possible. But they are unlikely to be achieved unless the United States is willing to address points of Russian concern. Given all that is at stake, we believe comprehensive discussions are a necessity as we work our way toward ever more significant nuclear disarmament.

William J. Perry, a senior fellow at the Freeman Spogli Institute for International Studies, was the secretary of defense from 1994 to 1997. George P. Shultz, the secretary of state from 1982 to 1989, is a distinguished fellow at the Hoover Institution.