Like an elephant stampeded by a mouse, the United States is being driven toward increased danger by the fear that North Korea or Iran could soon acquire nuclear-armed missiles capable of reaching this country. A U.S. national missile defense system is in development, and a deployment decision on a "thin" defense against a small number of missiles is scheduled for July 2000.

The desire for both prestige and bargaining leverage may motivate North Korea and Iran to acquire intercontinental ballistic missiles. But these missiles are unlikely vehicles for a deliberate nuclear attack--unless a country wants to commit suicide. The attacker's identity would be far easier to conceal if a boat or civilian aircraft were used.

It might make sense to invest in a missile defense "just in case"--if the costs were only monetary. But as Chinese, Russian and West European officials have warned repeatedly and publicly in recent months, U.S. deployment of a national missile defense would have more far-reaching consequences.

China's military has noticed that the first antimissile base, proposed for Alaska to intercept a potential future threat from North Korea, is also positioned to shield against China's small intercontinental missile force. The Chinese government fears that this might give the United States more freedom to back Taiwan if that island were to declare independence.

China's response to a deployment decision would likely be to build more nuclear-armed missiles capable of reaching the United States. This would move the United States toward a large-scale missile confrontation with China similar to the one with Russia which we are finding so difficult to dismantle.

Russia's military, meanwhile, is worried about the vulnerability of its land-based missiles to attacks by an expanded NATO equipped with the precision-guided non-nuclear missiles and bombs demonstrated in Iraq and Yugoslavia. This insecurity is compounded by the fact that Russia can no longer afford to keep its ballistic-missile submarines hidden at sea. Russia's missile generals see the proposed U.S. system as a first step toward construction of a shield against the small retaliatory strike that Russia could mount after a U.S. first strike.

To ensure that any American missile defense could be overwhelmed, Russia would keep as many nuclear warheads on hair-trigger, launch-on-warning alert as possible. This would increase the risk of an accidental or unauthorized Russian launch, arguably already the greatest threat to U.S. national survival.

Ironically, standard military worst-case assessments of a U.S. national missile defense by the Russian military could evoke these reactions even if more realistic analyses indicated that the missile defense would be unlikely to intercept even a few warheads. (Although a U.S. missile defense could eventually be tuned to work against U.S. target test missiles, few experts believe it would work the first time against foreign missiles equipped with even simple countermeasures.)

If the United States deployed missile defenses, Chinese and Russian missiles would certainly be equipped with countermeasures. As a result, even a few missiles, launched accidentally or without authorization, could penetrate the system. This simple fact has, in the past, sufficed to convince the United Staes that it would be pointless to deploy missile defenses.

Negotiating a START III agreement with Russia would be a far more effective way to reduce the nuclear threat to the United States. Such an agreement would allow almost 4,000 Russian missile warheads to be removed from their launchers by the end of 2007.

This comparison between missile defense and negotiated reductions illustrates the difficult truth that each American administration has had to relearn: The most effective protection against nuclear weapons is to strengthen the nuclear nonproliferation and disarmament regime in cooperation with other like-minded nations. As both Russia and our West European allies have emphasized, these cooperative efforts would most likely be derailed by a U.S. decision to go it alone in pursuit of illusory defenses.

Bill Bradley has thus far been the only presidential candidate to warn against a precipitous decision on national missile defense. He has also broken ranks by advocating that the United States respond to Russia's concerns about the unequal impact of START II by agreeing to begin negotiations on deeper START III cuts.

Other national politicians should follow Bradley's example and think again about the momentous choice between missile defense and missile reductions. If they do not, the undoing of post-Cold War reductions of the nuclear danger is all too predictable.

Philipp Bleek is with the Federation of American Scientists. Frank von Hippel is a professor of public and international affairs at Princeton University.