START is stopped.

That is not all bad, because the Strategic Arms Reduction Treaty has been overtaken.We need a new approach to nuclear arms control that takes account of the growing prospect of prolonged civil strife in the Soviet Union, where more than 25,000 nuclear warheads could be captured or stolen.

The best alternative to another round of prolonged negotiations about which weapons each side might give up would be for President Bush to announce a unilateral reduction of America's 25,000 long- and short-range nuclear warheads down to, say, 10,000.

This would place immense pressure on Mikhail Gorbachev to follow suit, for political and economic reasons.

Would he do so at this time?

Gorbachev is apparently increasingly beholden to his military.

Yet, a few months ago, when I discussed this idea with a senior Soviet military officer in Moscow, he saw no obstacle to either president's initiating unilateral reductions.

This single, informal response certainly does not give assurance as to how the Soviet government would react, but it does indicate that the door would not be shut automatically.

And, in contrast to most Soviet concessions on armaments in recent years, this program would not involve greater reductions on the Soviet side than on ours: The marshals and admirals need not feel humiliated.

What if Gorbachev did not follow our lead?

I told my Soviet contact I would not worry: "I do not believe that you, sir, could advise your president that it would be safe to attack the United States even if you had 25,000 warheads and we had only 10,000."

His response was instant agreement: "Da."

The beauty of moving unilaterally is that we could induce early and substantial reductions of the Soviet arsenal without waiting to iron out details that have come painfully slowly in the past.

If we went much below 10,000 we would need to work out the details of verification, but there would be plenty of time to do that.

Skeptics on our side would fear nuclear "inferiority."

They might say by throwing away 15,000 warheads the United States could no longer target the entire Soviet arsenal.

But how realistic has it ever been to think of launching anything like 25,000 warheads?

The world would be at risk.

At 10,000 warheads of our own choice, we could not only deter a major nuclear attack, we would still be prepared for small or accidental nuclear attacks - regardless of how many warheads the Soviets retained.

Finally, the skeptics might doubt that Bush would want to take the political risks associated with such a unilateral move.

But having just clearly demonstrated his willingness to use appropriate force when needed, Bush is in an ideal position to make an imaginative move for peace and security.