At Summit Arms Discussions, It Will Be a Whole New Ballgame : Nuclear arsenals: Major unilateral reductions have been announced. Bush and Gorbachev must now decide what kind of cuts to make in long-range missiles.

When George Bush and Mikhail S. Gorbachev meet Tuesday in Madrid, one of the issues on their agenda--as at every U.S.-Soviet summit since the 1950s--will be the quandary of controlling the thousands of nuclear weapons the United States and the Soviet Union have aimed at each other.

But this time, while the weapons are the same, the landscape has changed, and that has made all the difference.

Only three months ago, the United States and the Soviet Union were still locked in the old-fashioned brand of arms-control negotiations, haggling eyeball-to-eyeball over the fine print of a 500-page-long Strategic Arms Reduction Treaty that took nine years to produce.

Then came the Soviet Union’s abortive military coup last August and the political revolution that followed.

Ever since, U.S.-Soviet dealings over nuclear arms--the doomsday weapons that the two superpowers built to create a balance of terror--have changed from high-tech hardball into what one arms control-expert cheerfully calls a “competitive striptease.”

“It’s as different as night and day,” says Richard N. Perle, the hard-liner who molded the Reagan Administration’s nuclear weapons policies. “Since August, the Cold War has finally ended in arms control. There’s been a real sea change. . . . The weapons are still there, but there’s no reason to lose sleep over them anymore.”

“The change is enormous,” agrees Robert S. McNamara, who was secretary of defense during the Johnson Administration. “The whole intellectual foundation for strategic nuclear forces is being re-examined.”

Beginning with an initiative by President Bush last month and a reply from President Gorbachev three weeks ago, the two leaders have ordered a series of sweeping unilateral arms cuts and made additional proposals that would reshape their arsenals still further.

The cuts so far have mainly been in the short-range nuclear weapons that the two superpowers maintained for use in the European war for which they spent 40 years preparing--a war that is now unthinkable.

Bush announced that he was withdrawing all nuclear artillery shells and short-range missiles from both ground and naval forces; Gorbachev matched the move and proposed destroying most of the weapons involved.

“This is the most important change since the 1950s,” a Soviet arms-control specialist says. “. . . All this is being abandoned so fast that it is dizzying.”

The Madrid summit will be the two presidents’ first face-to-face meeting since those unilateral cuts, and officials in both Washington and Moscow expect them to spend some time discussing where to go from here.

In particular, Bush and Gorbachev must consider what kind of cuts to make in long-range missiles, the weapons that are the centerpiece of each country’s offensive nuclear force.

For the first time ever, officials in both governments are seriously considering rapid, deep cuts to levels far below the thousands of nuclear warheads they now hold.

Signs are that Gorbachev wants to move fast toward new reductions; he has already proposed a quick cut of 1,000 warheads from the ceiling of 6,000 that was set only three months ago in the START Treaty.

U.S. and Soviet officials say they expect Gorbachev to press the idea at Madrid. “President Bush’s initiative was very important and very timely, but it is not . . . the last word,” says Georgy A. Arbatov, Moscow’s veteran America-watcher.

Bush is moving more cautiously. Instead of suggesting a similar across-the-board cut, he has proposed banning missiles with multiple warheads--a longstanding U.S. idea that would require the Soviet Union to dismantle far more weapons than the United States.

Asked at a news conference last week if he was taking any new arms-reduction proposals to the summit, the President answered bluntly: “No.”

The Madrid meeting “isn’t meant to be a negotiation,” a Bush aide explained. “There have been arms-control initiatives on both sides, and we will talk about what each side is doing to implement those initiatives.”

But other U.S. officials predict that Bush will have to respond with more forthcoming steps. “Gorbachev is going to try to put pressure on us, and he’s very good at that,” says one.

And Soviet officials say they are relying on the United States to move things forward. “We are not capable of true initiatives,” a former Soviet arms negotiator confesses. “We do not have a government capable of making the necessary decisions.”

Indeed, the biggest changes on the arms control scene don’t stem from missile cuts or disarmament proposals; they come from the new political realities in the Soviet Union.

The August revolution removed most of the Cold War Old Guard that ran the Soviet defense Establishment and insisted on maintaining a huge nuclear force as evidence of the nation’s superpower status.

The aftermath of the coup sent the Soviet Union’s 15 republics hurtling toward independence, making control of the Soviet nuclear arsenal a major concern in both Moscow and Washington.

And the disintegrating Soviet economy made it ever clearer that the Kremlin could no longer keep up with the United States in developing and building advanced nuclear weaponry, compelling Gorbachev and his military officers to seek mutual arms reductions as quickly as possible.

“The political changes in the Soviet Union have made all the difference,” says Kenneth L. Adelman, director of the U.S. arms-control agency during the Reagan Administration. “There really is a desire to get rid of arms systems over there. . . . What has happened in the three months since START is more dramatic, in terms of the safety of the world, than the nine years of negotiations that came before.”

U.S. officials say Bush and Gorbachev won’t have time during their two-hour summit lunch in Madrid to hold detailed discussions. But here are the main issues that will be on the table:

Long-range missiles: The Soviets, plus an increasing number of U.S. arms experts, want radical cuts in the number of long-range warheads, but the U.S. defense Establishment isn’t ready for that. “We can go lower, and I think we should,” says Perle.

McNamara and other U.S. experts have suggested that each side could now maintain stable nuclear deterrence with only 1,000 warheads (instead of more than 6,000 each under START). Soviet nuclear physicist Yevgeny Velikhov has suggested 200 warheads each.

Instead, the Bush Administration has proposed banning all land-based missiles with multiple warheads on grounds that they are the most dangerous offensive weapons and the most inviting nuclear targets. The Soviets have objected to that idea because those missiles are more important to their nuclear force than they are to the U.S. force; a ban would affect about 2,500 Soviet warheads, but fewer than 950 U.S. warheads.

If the Bush Administration’s current proposal were implemented, one U.S. official notes, it could require the Soviets to build hundreds of new single-warhead missiles to replace the banned multiple-warhead kind. “That would break the bank,” he says.

Instead, he suggests, the Soviets will probably propose a compromise that blends the two proposals.

Nuclear defense: The Reagan Administration’s plan to develop defenses against nuclear attacks--derided as “Star Wars”--once drew such fierce opposition from Gorbachev that he warned it would stand in the way of any arms agreements. Now the Soviet president says he is willing to discuss U.S.-Soviet cooperation in the field.

Two things have changed. First, the Bush Administration has scaled down the once-ambitious Strategic Defense Initiative and is concentrating on a system to protect against limited missile attacks from terrorists, accidental launches or smaller powers. Second, Soviet strategists have become increasingly concerned about their vulnerability to missile attacks from the Third World instead of from the United States.

At a seminar here, Soviet Maj. Gen. Alexander I. Vladimirov praised the Bush Administration’s approach as “a manifestation of good sense, wisdom and statesmanship” and called for a “condominium of sensible people from the Soviet Union, the United States and Europe” to neutralize nuclear threats from “the bits and pieces” of the Third World.

Henry Cooper, director of the American SDI effort, calls the apparent Soviet turnaround “breathtaking.” “The important thing is the high-level commitment to talk about these things,” he says. “If that happens, I’m confident you can work the rest out.”

But U.S. officials and experts are divided over whether the Soviet shift is serious--and said they hope Gorbachev will provide some answers to Bush in Madrid.

One Soviet official portrays the change as largely tactical, made in hopes of eliciting U.S. cooperation on missile cuts and other issues.

“To get enough give . . . we said, ‘Well, maybe, let’s take a look at a limited SDI,’ ” the official says. “We needed a forthcoming position--that was our mandate from Gorbachev--and we did not want a quarrel on SDI to undercut progress on other matters.” Real Soviet cooperation, he says, will depend on how limited the system would be and on how much technology the United States is willing to share.

Other issues: In his response to Bush earlier this month, Gorbachev announced that he is ending Soviet production of plutonium, the basic material of nuclear explosives; declared a one-year moratorium on nuclear weapons tests; reaffirmed the traditional Soviet pledge not to be the first country to use nuclear weapons, and challenged Bush to follow suit on all three.

Last, Bush’s national security adviser, Brent Scowcroft, proposed that Bush take positive responses to Madrid on all three issues. But Defense Secretary Dick Cheney objected, officials say.

Scowcroft’s suggestion would have provided Bush with the kind of bold stroke he likes to take without being too radical, one official says. On the “no first use” issue, for example, Scowcroft was apparently embracing only the idea of holding U.S.-Soviet talks on the proposal rather than providing an immediate U.S. endorsement.

But any of the three would have been a marked departure from previous U.S. practice. “It would have shaken up the bureaucracy, and the bureaucracy wasn’t ready for it,” one official says. Bush probably won’t bring up the ideas at Madrid, but they will probably resurface later, he says.

Meanwhile, the Soviets have shown new flexibility about accepting U.S. arguments that some nuclear testing is a good thing because it helps develop safer and more reliable weapons. Arbatov suggests that the two countries form a joint scientific commission to study the need for continued testing and to assess its impact on the environment. “Let the scientists examine the issue together, objectively, and have their say,” he says.

Control of nuclear forces: There is one issue Bush and Gorbachev agree on; the Soviet Union’s nuclear weapons should remain under the control of the central government in Moscow, not the fractious regimes of the 12 remaining republics.

Last week, the Bush Administration launched a pointed warning toward the secession-minded government of the Ukraine, saying that the United States would neither recognize nor aid an independent regime in Kiev if it tried to take even partial control over the nuclear weapons on its territory.

“We need to convince the republics that this is something we will not brook,” a State Department official says.

McManus reported from Washington and Parks reported from Moscow. Times staff writer Melissa Healy also contributed to this article.