WASHINGTON — Secretary of State George P. Shultz's trip to Moscow this week is shaping up as a crucial--some say "make-or-break"--meeting on a new agreement to reduce long-range offensive nuclear arms in the final year of the Reagan Administration, according to U.S. officials.
Accompanied by Frank C. Carlucci, the President's national security adviser, Shultz will also try to set a date for a U.S. visit by Soviet leader Mikhail S. Gorbachev to sign a treaty banning intermediate-range nuclear missiles.
Such a treaty, nearing completion in arms negotiations in Geneva, would be modest compared with an agreement to curb the gigantic long-range missiles the two sides are prepared to hurl at each other.
Strategic missiles have a range of at least 3,000 miles and are capable of striking targets anywhere in the United States or the Soviet Union from U.S. and Soviet launch sites. Intermediate-range missiles are designed to strike targets between 300 miles and 3,000 miles from launch sites.
The superpowers have agreed in principle to cut their offensive arsenals in half, to a ceiling on each side of 1,600 delivery systems (missiles and bombers) and 6,000 warheads on those systems. And Gorbachev has said a treaty can be signed in the first half of 1988.
2 Breakthroughs Required
But two breakthroughs, requiring political decisions at the highest level, are needed before Gorbachev's timetable can be achieved. They involve:
-- Soviet demands for limits on President Reagan's Strategic Defense Initiative, the space-based missile-defense system commonly known as "Star Wars." The Kremlin has long demanded constraints on SDI as a condition for deep cuts in offensive nuclear weapons, but it recently appears to have eased away somewhat from linkage.
"If Soviet concerns are to achieve predictability (in U.S. anti-missile efforts), we can do business," a senior White House official said in an interview. "But if they are still out to stop SDI, then we can't."
-- U.S. demands for limits on Soviet missiles, the number and accuracy of which create the capability for a surprise attack. The United States has proposed a limit of 4,800 ballistic missile warheads of all kinds, with a maximum of 3,300 on land-based missiles.
"If Shultz can get Soviet acceptance of the 4,800 number in Moscow, he will be prepared to make concessions on other things," a senior Administration official said.
Starting with the visit here last month by Foreign Minister Eduard A. Shevardnadze, the Soviets have shown new flexibility on both issues. But opinion is divided on whether they are ready to go far enough.
The consensus in the United States is that while the Soviets are prepared to move ahead faster toward an offensive weapons agreement without parallel advances in the missile defense negotiations, they are reserving the option of stopping short of actually signing an agreement in the absence of limits on SDI.
Some State Department officials are more optimistic. They believe the Soviets will "climb off" the linkage--deep cuts in offensive weapons only in combination with constraints on SDI--when Shultz gets to Moscow. But several senior Administration officials doubt that the Soviets will give up their effort to restrain SDI.
The recent Soviet flexibility, they note, could be a tactical move, designed less to reach a new accord on offensive weapons than to ensure congressional ratification of the expected treaty banning medium-range missiles. For Congress, the prospect of a 50% cut in long-range offensive weapons will be a major impetus to approve the medium-range accord.
Congressional rejection of that agreement would be nearly disastrous for the arms control process and for U.S.-Soviet relations. Gorbachev's position within the Kremlin would suffer a major blow, according to State Department analysts. More important, perhaps, disillusioned North Atlantic Treaty Organization allies of the United States might push for withdrawing medium-range U.S. missiles from their territory even without a treaty formally committing the Soviets to elimination of their medium- range missiles from Europe.
By and large, however, top U.S. officials believe the Soviets sincerely want a long-range weapons accord--dubbed START, for strategic arms reduction talks--with the Reagan Administration.
"They have told us they want to deal with a conservative Administration now rather than wait for the next one," the senior White House official said.
To exploit the perceived opening in the space defense negotiations, the Administration has put together a "predictability package" that would allow work on SDI to continue but would rule out deploying an anti-missile shield in space for seven years, one State Department official said.
The package would allow each side to observe the other's research efforts and tests of anti-missile devices. In addition, it would establish an annual information exchange that would describe work planned for the next year.