MOSCOW, OCT. 23 -- In a surprising rebuff at the end of two days of U.S.-Soviet meetings here, Soviet leader Mikhail Gorbachev told U.S. Secretary of State George P. Shultz that he was not prepared to set a date for a summit meeting in the United States because he is not satisfied with President Reagan's refusal to put limits on his antimissile defense program, commonly known as "Star Wars."

It had been widely expected that an agreement eliminating medium- and shorter-range offensive nuclear missiles on both sides would be completed here and an announcement made that the treaty would be signed at a Washington summit meeting later this year.

But Shultz, who announced the surprising news at the end of the talks, said Gorbachev "is apparently not yet satisfied, particularly in the area of space and defense," that progress in arms control justifies a visit to Washington.

The disappointing outcome stunned the U.S. delegation. There was no clear understanding of why the Soviet leader appeared to back away from the anticipated summit at the last moment after steady progress had been achieved earlier in the Moscow talks.

U.S. negotiators had thought, based on many earlier signals from Moscow, that agreement on a treaty banning medium-range and shorter-range missiles would be sufficient to justify a summit meeting this year.

But in an apparent hardening of the Kremlin's conditions for a summit in Washington, Soviet Foreign Minister Eduard Shevardnadze said tonight that holding such a meeting would require key provisions for reducing arsenals of strategic missiles, meaning those of intercontinental range, and strengthening the 1972 U.S.-Soviet Anti-Ballistic Missile (ABM) Treaty.

"If we get the key provisions then there will be no problem for a summit and the signing of a treaty on medium- and shorter-range missiles," Shevardnadze said at a press conference following Shultz's.

Shevardnadze said that the gap between the two sides over a medium-range missile treaty could be resolved "in three weeks," but added that the Soviet Union views a summit as a forum more for narrowing differences over space and strategic agreements than for signing an accord on what are called intermediate-range nuclear forces (INF).

He said such an accord could be signed when completed, but added that "the conditions, where and when, that remains to be determined."

The Soviet news agency Tass further explained that Gorbachev had told Shultz he now wants to "record an accord on the key provisions of future agreements on strategic offensive arms and space" at the same time the treaty on medium-range and short-range missiles is signed.

A preliminary accord on strategic arms and space weapons at the summit would then pave the way for final agreements to be "signed during Ronald Reagan's reply visit to the Soviet Union" next year, Tass said.

There were differences of opinion among members of Shultz's negotiating team about why the setback came about and how serious it will turn out to be. One senior official said that the Soviets seemed to have hardened their positions in several areas and speculated that Gorbachev may be facing unexpected domestic pressures. Objections to a summit centering largely on a medium-range missile accord may have arisen at a Central Committee plenum held suddenly on the eve of Shultz's visit, the official said.

The prevailing view among western diplomats based here, however, is that failing to set a date for the summit and leaving a missile accord in limbo is part of a Gorbachev strategy to pressure the Reagan administration into a compromise deal limiting research on the Strategic Defense Initiative antimissile defense system.

Gorbachev used similar tactics at a summit with Reagan in Reykjavik, Iceland, a year ago. The meeting eventually broke down without agreement because of a dispute over Reagan's plans to build a defense shield against nuclear weapons.

In his meeting with Shultz today, Gorbachev left a small possibility that he would stick to a U.S.-Soviet agreement made a month ago to hold a summit this fall.

"I am ready to visit the United States," he said, according to Tass. "But so far I am put on my guard by possible results."

Shevardnadze said that during his visit to Washington last month he and U.S. officials had discussed a visit by Reagan to Moscow in the first quarter of 1988 in addition to the tentative plans for a fall summit in Washington.

In a 4 1/2-hour meeting at the Kremlin this morning, Gorbachev told Shultz he would be sending a letter to Reagan. In the letter, Gorbachev plans to outline new Soviet proposals to reduce strategic weapons and Moscow's position on limiting space research, and he will appeal for a similar outline of Reagan's personal views on the subjects, Shevardnadze said tonight.

Both sides reported success in resolving a dispute over the West German-based Pershing IA missiles and considerable progress in narrowing other differences over a missiles accord. The main outstanding obstacle is over the terms of verifying the gradual elimination of the missiles, U.S. and Soviet officials said tonight.

Gorbachev today proposed a ban beginning Nov. 1 on the production, testing and deployment of all medium- and shorter-range nuclear arsenals on both sides, Tass reported.

Gorbachev also softened the Soviet stance on proposed cuts in strategic arsenals. Shevardnadze quoted the party leader as saying that a strategic arms limitation accord could limit the land-based intercontinental ballistic missile warheads to between 3,000 and 3,300 for each side. The United States has already proposed limits similar in number but different in detail.

U.S. officials said it was a positive move for the Soviets to return to the idea of "sublimits," which they had rejected recently. The figures given would seem to limit U.S. military forces in an unacceptable way. One official even described the Soviet proposal as a step backward.

Gorbachev also proposed limiting submarine warheads to between 1,800 and 2,000 and air-launched missile warheads to between 800 and 900.

Despite the concessions, Shultz and Shevardnadze both said that the key difference between the two sides is over the antiballistic missile treaty and both depicted the dispute as significant. Signed by both countries in 1972, the treaty establishes the terms under which research on space-based weapons can be conducted.

In his hour-long press conference Shultz staunchly defended the administration's position that space defense weapons are a necessary safeguard against a ballistic nuclear attack.

"We in the United States -- the president -- feel we must do everything to protect ourselves against ballistic missiles," Shultz said.

He said that both sides had made proposals on the subject but added that "they don't seem quite compatible. Maybe our objectives are not compatible."

The United States argues that the broad interpretation of the ABM treaty allows for testing of the components of an antiballistic missiles system in space. Moscow considers such a move a violation of the treaty.

"The major obstacle," Shevardnadze said tonight, "is the attitude {of the United States} to the ABM treaty."

In a meeting Sept. 15 to 17 between Shevardnadze and Shultz in Washington and in other recent contacts between the two sides, the Soviet Union had appeared to close the differences between the two sides over the issue.

In a press conference in Helsinki before coming to Moscow, however, Shultz had balked at the Soviet proposal.

"The more we try to pin it down," Shultz said, "the less there seems to be there."

According to Tass, Gorbachev also told Shultz that he would immediately begin a one-year moratorium on further construction of a large Soviet radar station near Krasnoyarsk, which the Reagan administration has called a violation of the Anti-Ballistic Missile Treaty.

Tass said the aim of the proposal was to strengthen "the atmosphere of trust" between the two countries and discourage "any talks that the Soviet Union allegedly violates the ABM treaty." It also quoted Gorbachev as seeking "a similar step" on a new U.S. radar station being constructed near Fylingdales Moor in England, which the Soviets have called an ABM treaty violation.

The United States denies that the radar station in England is a violation of the treaty and rejects comparisons between it and Krasnoyarsk. The Reagan administration also disagrees with Soviet proposals that the two sides adhere to the ABM treaty for 10 years, preferring a shorter period.

Tonight Shultz said Reagan and his advisers did not think the United States should give up the ability to "pursue the research necessary to move ahead with defending ourselves against ballistic missiles."

In a discussion between Gorbachev and Shultz today on the Persian Gulf crisis, the Soviet leader took a surprisingly conciliatory view of the U.S. role in the region. Although the U.S. military buildup in the gulf had not helped matters, he was quoted as saying, "the argument that it was necessary to ensure the supply of oil is understandable to us." Gorbachev also said that the constructive U.S.-Soviet approach to the Iran-Iraq conflict had helped lead to the United Nations call for a cease-fire.