Bill Clinton's forthcoming decision about whether to proceed with national missile defenses (NMD) is the subject of growing controversy in the US. By contrast, there is almost no controversy about NMD in Europe, Russia, or China, where almost everyone seems to believe that it is a bad idea.

Given the political and security interests at stake, it is in everyone's interest to find ways to bridge these differences. But it is essential that governments do not lock themselves into positions that have the effect of transforming concerns about stability and arms races into self-fulfilling prophecies. Critics of missile defenses have a plan to avoid these pitfalls: simply postpone a deployment decision. In a narrow sense, they are right: no-one would argue that national missile defenses should get the green light unless and until there is reasonable confidence that the system will work.

There also is some merit to suggestions that Mr Clinton leave the NMD decision to his successor rather than make such a momentous call in the waning days of his presidency. Such proposals, however, overlook the fact that deferring the decision by only a few months would delay deployment by at least a year.

Lurking behind these arguments about timing is the concern that a US decision to proceed with missile defenses would be strategically destabilising. Europeans, Russians and Chinese, however, have different reasons for reaching this shared conclusion. Indeed, Europeans tend to have two somewhat contradictory objections to NMD. Some argue that missile defenses are unnecessary because the ballistic threat from rogue states is not that serious and/or can be deterred by the same threat of retaliation that served us so well during the cold war. To proceed with NMD, they assert, would be not only a waste of defense resources, but also a dangerous provocation to Russia. Invoking a different cold war analogy, others argue that the threat is real, but that a US decision to protect its homeland from ballistic missile attacks by rogue states would "decouple" its security from that of its allies.

Moscow's stated objections centre on the suspicion that

American missile defenses will sooner or later undermine the credibility of the Russian strategic nuclear deterrent. It asserts that it will have no choice but to respond by taking steps that could have the effect of putting its current nuclear forces on a more dangerous footing, or of launching a new arms race.

The Chinese (correctly) observe that virtually any missile defense system big enough to defend against even a fledging North Korean threat would degrade the credibility of China's current strategic nuclear deterrent. And so we should not be surprised - much less regard it as clear evidence of hostile intent - if China responds by expanding its strategic nuclear forces.

What is perhaps most striking about many of the objections to missile defenses, however, is that they seem to derive from outdated cold war paradigms. Today the US, along with its former adversaries and longtime allies, face a new common threat: the proliferation of weapons of mass destruction.

Responding to this new threat demands fresh thinking about the relationship between nuclear offences and nuclear defenses. In a world in which the US and Russia are no longer nuclear adversaries, missile defenses are not intrinsically destabilising.

On the contrary, limited defenses should be viewed as being entirely consistent with the purposes and objectives of the Anti-Ballistic Missile Treaty. In such a post-cold war world, missile defense deployments need not spawn a new nuclear arms race, but instead could - and perhaps should - be accompanied by reductions in strategic offensive forces.

Nor should national missile defenses be regarded as a unilateral US response to a peculiarly US problem that comes at the expense of the interests of others. Missile defenses could be deployed in Europe to protect Nato countries from rogue states. There is also ample room for mutually beneficial co-operation with the Russians.

It will take time to create an impulse to co-operate, to translate that impulse into concrete programmes with the US's European allies and Russia, and to deal with ABM Treaty issues. In a perfect world, this might counsel that the US postpone a decision on NMD. But in the real world betting that the threat will wait would be a risky. It also is important to note that it will take at least five years following a deployment decision before the US will be able to field even very modest missile defenses.

Those same five years, however, provide an opportunity to find common ground. Whatever Mr Clinton decides this summer should mark the beginning, not the end, of these efforts. The alternative is a dangerous self-fulfilling prophecy that would constitute the real threat to stability.