The Soviet leadership has told the United States and a senior Kuwaiti official that it is "cautiously optimistic" about the situation in the Persian Gulf following the visit this week of a special Kremlin envoy to Baghdad.

U.S. officials said, however, that there appeared to be no substantive progress toward ending the war. "There was no real glimmer of a shift in {Iraqi President} Saddam Hussein's position," said one administration policy-maker.

"As far as I understand from the Soviet leadership, the Soviet envoy met with some flexibility from the regime in Baghdad," Kuwaiti Foreign Minister Sabah Ahmed Sabah told reporters in Moscow.

Yevgeny Primakov, a special envoy of President Mikhail Gorbachev, told Soviet television after his return from Iraq on Wednesday that while a cease-fire did not appear to be imminent, "there are rays of light that enable us to think more optimistically." He did not elaborate.

Soviet Foreign Ministry spokesman Vitaly Churkin cautioned reporters: "Don't jump to conclusions. This is a very cautious optimism, nothing solid we can grab onto to give hope for a speedy outcome."

Soviet Foreign Minister Alexander Bessmyrtnykh telephoned Secretary of State James A. Baker III on Wednesday to talk about the Primakov mission and arms control issues, the State Department announced. Late Wednesday night, Baker received from Soviet officials a written report on the Primakov trip which generally echoed the envoy's public statement that there were optimistic signs.

Administration officials said yesterday, however, that there was little evidence in the Soviet report to suggest Saddam is preparing to relinquish Kuwait, as demanded by the international coalition.

"The Soviets are not any more genuinely hopeful than we are that anything is going to come of it," the administration policy-maker said. "The Soviets are trying to accent the positive and preserve the appearance of an actual search for a solution."

A second U.S. official familiar with the Soviet report said: "If they saw any flexibility, it is in tone and body language. Does that translate into leaving Kuwait? Who knows?"

State Department spokesman Margaret Tutwiler said Baker "doesn't want to characterize whether he thinks it's promising or not promising. His view is, basically, that it remains to be seen if there's anything there."

Administration officials recalled that Primakov had made a similar upbeat statement after meeting Saddam last fall. But they have been careful not to criticize the Soviet diplomatic efforts, in part because of the Soviet Union's changing domestic politics, in which hard-liners have become resurgent, and because the United States still wants the Kremlin's cooperation in the gulf.

Moscow has suddenly become a center of intense diplomatic activity on the gulf war. Iran's Foreign Minister Ali Akbar Velayati is to meet with Gorbachev here today, and Iraqi Foreign Minister Tariq Aziz is scheduled to arrive Sunday. Velayati and Aziz, however, are not expected to meet.

Velayati said in Geneva yesterday that he is flying to Moscow to discuss a new Soviet peace initiative. He said Iran does not have a peace plan but "only ideas," and he said he hoped to talk with the Soviet leadership about a cease-fire.

Velayati, in Geneva to address the United Nations disarmament conference, said Iran remains committed to Iraqi withdrawal from Kuwait as a prerequisite for peace, but added that it should be accompanied by the pullout of all foreign forces from the region. He also criticized the bombing Wednesday of a structure in Baghdad in which scores of civilians were killed.

U.S. officials said they are particularly interested in the outcome of the Aziz visit to Moscow this weekend. They noted it was the first time he has gone abroad since the war began, and they recalled the chilly reception Aziz received from the Soviet leadership on a visit last fall. "Is this really a show-and-tell by the Iraqis, or are they really shook up and serious?" said a State Department official. "And how are the Soviets going to use this?"

Churkin was guarded about prospects for the meetings, saying, "We have no strategy that would go beyond the U.N. Security Council resolutions. Our objective is, as we see it, to persuade Iraq to withdraw from Kuwait, that there is no other way out."

Churkin said Primakov "did talk to Saddam Hussein and spoke very forcefully to him and we hope that Tariq Aziz will bring a positive response to those representations. There are a lot of things in that very strong representation that {Primakov} brought to Baghdad which we feel ought to convince Saddam to withdraw from Kuwait, but we cannot be sure of the reaction."

When asked whether the Kremlin was trying to negotiate a settlement in the gulf, Churkin repeated Foreign Minister Bessmertnykh's statement earlier this week: "The Soviet Union is a mediator between war and peace."

Although Gorbachev has distanced himself somewhat from the Bush administration's decision to bomb Iraq, the Soviet Union has restated its allegiance to the U.N. coalition against Baghdad and the Kuwaiti foreign minister said he was satisfied with Moscow's position.

According to the official Soviet news agency Tass, Gorbachev told the Kuwaiti that Primakov had made clear to Saddam in Baghdad that there was no sense in trying to divide the U.N. coalition.

When asked about Wednesday's bombing of the bunker, which prompted anger in Iraq and other Arab countries, Churkin gave an answer clearly designed to avoid conflict with Washington.

"We are not umpires here," he said. "The {civilian deaths} confirm the Soviet concerns that the logic of war can bring about unpredictable circumstances and the situation can get out of hand."

But Tass ran a commentary critical of Washington, saying the civilian deaths in Baghdad bore out warnings from Moscow and elsewhere that the bombing campaign would lead to such tragedies. Tass said there have been "thousands" of civilian deaths since the war started last month.

The government newspaper Izvestia, in a commentary, stressed the need for Moscow to "distance itself from the actions of Washington," so the Soviet Union might resume working relations with Arab countries after the war.

More hard-line newspapers, especially Sovyetskaya Rossiya, have been sharply critical of Gorbachev's policy, saying Moscow is supporting a "neocolonial adventure" in the Middle East that will leave the Soviet Union without any allies in the region.

Sovyetskaya Rossiya yesterday printed letters from young men who wrote to the Iraqi Embassy here expressing political support and even a willingness to join the fighting on Iraq's side.

"I'm a reserve officer, and I not only sympathize with Iraq, I'm completely on your side," wrote N. Gribakon from Poltava. "I ask you to enlist me as a volunteer for the just struggle against American imperialism."Remnick reported from Moscow; Hoffman from Washington. Special correspondent John Parry in Geneva contributed to this report.