When NATO leaders meet in Chicago May 20-21, they will announce that the Alliance’s missile defense system has achieved an interim operational capability. That in large part reflects implementation of the first phase of the “European phased adaptive approach” (EPAA) announced by the Obama administration in 2009: in 2011, U.S. Navy warships with the Standard SM-3 interceptor began operating in the eastern Mediterranean, and a U.S. missile defense radar was deployed to Turkey.

What will be missing is agreement on a NATO-Russia cooperative missile defense arrangement. Russian President Putin will not come to Chicago. Although U.S. and Russian views on how a cooperative arrangement would operate converge significantly, Moscow’s call for a “legal guarantee” that U.S. missile defense systems would not be directed against Russian strategic missiles has stymied agreement.

Why does cooperation make sense for Washington and NATO? First, it would defuse missile defense from becoming a problem that would undermine broader U.S.-Russian and NATO-Russian relations. Second, involving the Russians would provide a better defense of Europe. Third, genuine cooperation could prove a game-changer in knocking down lingering Cold War stereotypes in Moscow.

What is the problem with the Russian demand for a legal guarantee? The Russians say it should be accompanied by “objective criteria” such as limits on the numbers and velocities of interceptor missiles. It would amount to a treaty. Anyone who follows the Senate knows that anything that hints at limits on missile defense has zero chance of ratification. The Russians know this.

The Obama administration has offered a political commitment in lieu of a legal guarantee and argues that U.S. interceptors lack the velocity and range to threaten Russian strategic missiles. While the Russians have a legitimate concern that missile defense could at some point undermine the strategic balance, it is difficult to see current U.S. plans posing such a threat. But Moscow so far does not buy it.

Various motives underlie the Russian position. In particular, they seem to want to remain in a holding pattern until after the U.S. presidential election in November. That’s likely because they anticipate that a Romney administration would pursue a different course on missile defense than a reelected Obama administration. When one considers how the U.S. approach changed from Bill Clinton (explored a national missile defense) to George W. Bush (withdrew from the Anti-Ballistic Missile Treaty and rapidly deployed a rudimentary defense of the U.S. homeland) to Barack Obama (radically reconfigured the Bush plan for missile defense in Europe), a Russian decision to wait and see has an understandable rationale.

While perhaps understandable, the Russian position unfortunately blocks the reported progress by Pentagon and Russian Ministry of Defense officials on what missile defense cooperation would mean in practice. They have discussed transparency regarding missile defense capabilities, joint exercises and jointly manned missile defense centers. A “data fusion center” would take data from NATO and Russian sensors and combine them to provide a common operational picture, which could then be shared with NATO and Russian missile defense commands. U.S. officials are interested in access to data from Russian radars that could provide earlier warning of a ballistic missile launch from Iran. A “planning and operations center” would provide the venue for NATO and Russian officers to discuss possible threats and rules of engagement for defending against a missile attack.

This work, however, has been held up by the dispute over a legal guarantee.

With a view toward 2013, the United States and NATO should consider how to make it as easy as possible for Moscow to say yes to cooperation. They should reiterate the offer of a political commitment and transparency regarding U.S. and NATO missile defense programs, including the opportunity to observe U.S. Standard SM-3 tests. The Alliance should indicate that a cooperative arrangement could be time-limited, say to four years’ duration. If, at the end of that period, the Russians still held concerns about NATO missile defenses, they could walk away.

NATO and Washington, moreover, should adjust two points of their public stance on missile defense. First, NATO and U.S. officials repeatedly state that cooperation would in no way affect NATO’s plans. That reduces Russian incentives to agree to a cooperative system. The Alliance should instead say that it is open to Russian suggestions so long as those ideas do not degrade the ability of NATO’s missile defense system to defend NATO members. If that criterion can be met, the Alliance should look at Russian proposals with a flexible mindset.

Second, Moscow’s concern focuses most on phase 4 of the EPAA, to be achieved in 2020 or 2021 when the Standard SM-3 missile is to acquire capabilities to intercept intercontinental ballistic missiles (ICBMs). Washington should indicate that the “adaptive” aspect of the EPAA includes the possibility that phase 4 could be delayed if it became clear that Iran is not making progress toward an ICBM capability. That could have the added advantage of encouraging Moscow to use its diplomatic weight with Tehran to urge that the Iranians not develop an ICBM.

This kind of approach would position Washington and the Alliance well to test Russian readiness to cooperate. And it could open the path to a cooperative NATO-Russia missile defense arrangement that is in the interest of all the parties.