Defense Secretary Caspar W. Weinberger said yesterday that escort of Kuwaiti tankers by U.S. warships in the Persian Gulf is "imminent," and warned that Iranian missile installations will be attacked if the United States believes Iran is preparing to fire them.

But Weinberger insisted that the United States would not launch preemptive strikes against the Chinese-made, antiship Silkworm missiles Iran has deployed near the Strait of Hormuz at the mouth of the gulf. He defined a preemptive strike as an attack intended to destroy enemy weapons without regard to whether they were about to be used.

"Nobody's talking about preemptive strikes," he said during an interview with reporters from the Knight-Ridder newspapers that was broadcast by C-Span cable television network. He added:

"What we're talking about is responding to evidence of hostile intent, and that is an important distinction to bear in mind. But it is important also to know that we would not contemplate waiting until we actually received a hit."

While Weinberger was explaining U.S. plans in the administration's controversial effort to use military leverage in the Iran-Iraq war, the United States pressed ahead in trying to induce the U.N. Security Council to adopt a resolution ordering the countries to stop fighting.

Following weeks of U.S. lobbying, State Department officials predicted that the resolution calling for an immediate cease-fire will be ready for a vote this week. To underscore the U.S. view that the resolution is a potentially important weapon for forcing Iran and Iraq to the bargaining table, Secretary of State George P. Shultz plans to go to New York and participate in the debate when the resolution comes up for a vote.

Department spokesman Charles E. Redman said the draft resolution "demands an immediate cease-fire, discontinuation of all military actions and withdrawal to internationally recognized boundaries" in the war that began in 1980.

Redman, citing an "almost unprecedented level of agreement and cooperation" among Security Council members, said the draft differs from earlier U.N. resolutions on the gulf war that " 'called for' an end to fighting but did not order it." He noted that the draft resolution "demands an immediate cease-fire," and added:

"Thus, as a matter of international law, Iran and Iraq, as U.N. members, will be obligated to comply with the terms of the resolution. Failure to comply would make the noncomplying party liable to enforcement measures that can be ordered subsequently by the Security Council. While the draft resolution does not itself contain enforcement measures, it sets the stage for them."

The United States has tilted diplomatic efforts toward Iraq, which has made clear its willingness to accept a cease-fire while Iran insists on pursuing the war. The purpose of the resolution, diplomatic sources said, is to illustrate that difference. Thus, Iran will be isolated in a way that might make other countries willing to support such sanctions as an arms embargo.

Pentagon sources said yesterday the Navy is arming a group of Seasprite and Seahawk helicopters with machine guns and radar so that they can be based on U.S. ships escorting the Kuwaiti tankers.