Avoiding nuclear war is the most solemn, somber and awesome of all presidential responsibilities. Yet, throughout the long presidential campaign of 2000, nuclear weapons were barely a blip on the political radar screen.

Nevertheless the question facing President Bush and his new administration is real and pressing: What to do about the approximately 4,500 to 5,000 nuclear weapons in the Russian and American arsenals that remain -- 10 years after the Cold War -- on hair-trigger alert.

As incomprehensible as it may seem, we still live on the brink of nuclear war, with thousands of warheads ready to be fired in a matter of minutes. Nuclear war by accident or miscalculation remains a serious and very real threat. How could it happen?

According to "Dateline NBC," in September 1983, just weeks after the Soviet Union shot down Korean Airlines Flight 007, and with Soviet-American relations at a low ebb, Col. Stanislov Petrov was on duty outside Moscow monitoring nine Soviet satellites that were, in turn, monitoring U.S. nuclear missile bases. Shortly after midnight Col. Petrov's worst nightmare came true. Sirens sounded and his computer screen signaled the launch of a single U.S. missile (possibly carrying 10 nuclear warheads) just 30 seconds into its 25-minute flight to Moscow.

Petrov had to make an immediate assessment and relay it up the chain of command. If a full-scale U.S. attack was underway, the decision to retaliate would have to be made within minutes. All Petrov's systems appeared to be working properly. Remarkably, he reported to his superior that the alarm was false. Petrov reasoned that a U.S. attack would not begin with the firing of a single missile. It made no sense.

And then, within seconds, his computer detected the launch of four additional missiles causing alarms to sound at the Soviet Union's supreme command headquarters. The Soviets now had five minutes to "use them or lose them" -- that is, respond with a nuclear attack of their own or risk unilateral annihilation. But Petrov held firm -- he says he just didn't believe an attack was underway -- and assured those up the command that he was seeing a false alarm.

Had the Soviets launched under the pressure, U.S. retaliation would have been swift. Tens of millions would have been killed on both sides.

What prompted the false alarm? The satellite mistook sunlight reflecting off a cloud for the hot plume of a missile launch -- a software glitch. Petrov was not supposed to be on duty that night. Would another Soviet colonel have made the same assessment Petrov did?

The 1983 incident is not the only near catastrophe in recent times. In 1995 Russian radar mistook a Norwegian research rocket for an incoming U.S. ballistic missile speeding toward Moscow. President Yeltsin's nuclear "football" was activated. With only minutes to decide whether to launch a counterattack, it was determined that a U.S. attack was not imminent.

Today the combat-ready status of the Russian and U.S. nuclear arsenals keeps us poised on the brink. It need not be this way.

In a speech last May, then-candidate George W. Bush called for removing "as many [nuclear] weapons as possible from high-alert status." It is imperative that he work immediately with Russian President Vladimir Putin to do so.

De-alerting is made all the more urgent in light of the degradation of Russia's nuclear command and control systems over the past decade of economic and political turmoil there. De-alerting nuclear weapons increases the margin of safety by increasing the time that military and political leaders have to assess threats from minutes to days, or even weeks. It would, therefore, dramatically reduce the risks of accidental or inadvertent nuclear war.

De-alerting can be accomplished in several ways, some more readily verified than others. Warheads can be separated from their delivery vehicles (for example, removed from the missiles that carry them) and stored in secure areas. This is perhaps the most easily verified method and provides the greatest lead time before launch. Alternatively, switches used to fire missile motors can be pinned open, missile guidance systems or the pneumatic mechanisms that open missile silo covers can be removed, and/or explosion neutralizing wires can be inserted into the plutonium pits in warheads.

However it is accomplished, George W. Bush should act on his campaign promise to de-alert nuclear weapons quickly, because the next time a Russian or American president, or colonel, has to make the most fateful of all decisions, we may not be so lucky.

John O. Pastore is secretary and Peter Zheutlin associate program director of International Physicians for the Prevention of Nuclear War.