MOSCOW, AUG. 3 -- The Soviet Union and the United States, in an unprecedented joint statement on a major regional crisis, urged the international community today to halt arms deliveries to Iraq following its invasion of Kuwait.

The statement was issued at Moscow's Vnukovo airport after a 90-minute meeting on the crisis in the Persian Gulf between Secretary of State James A. Baker III and Soviet Foreign Minister Eduard Shevardnadze. Baker cut short his stay in Mongolia to fly back to Washington, stopping briefly in the Soviet capital.

Addressing a joint press conference in an airport lounge, the two ministers used similarly strong language against the Iraqi government of President Saddam Hussein, denouncing the its move Thursday into Kuwait as "crude," "tragic" and "a violation of international law." They then both read out a joint statement calling for the unconditional withdrawal of Iraqi troops from Kuwait and the restoration of the sheikdom's sovereignty and national independence.

"Governments that resort to glaring aggression should know that the international community cannot and will not reconcile itself to aggression," declared the statement, which was hurriedly drafted by Soviet and U.S. officials as Baker flew to Moscow from Ulan Bator, the Mongolian capital.

The U.S.-Soviet statement, and Baker's decision to return to the Soviet Union for further consultations with Shevardnadze only a day after the Iraqi invasion of Kuwait, marked a symbolic breakthrough in superpower cooperation on regional issues. The Soviet Union has long regarded Iraq as its most important ally in the Persian Gulf, supplying Baghdad with tanks, helicopters, fighter aircraft and small arms throughout the Iran-Iraq war of 1980-88.

Shevardnadze described the Kremlin's suspension of arms supplies to Baghdad as a "difficult decision" in view of the fact that "we have had good and longstanding relations with Iraq which have evolved for decades." He said that the Soviet Union had been forced to take such a step because the Iraqi invasion of Kuwait "contradicted the new thinking in international relations and the principles of civilized relations between nations."

Baker also emphasized the unusual nature of today's joint statement, saying that in the past both superpowers would have been likely to view such conflicts "through an East-West prism." He said: "The steps we have taken are a lot more than simply rhetoric. They are concrete actions."

Paradoxically, the outrage expressed by both Moscow and Washington over Iraq's invasion has also served to underline the impotence of the two superpowers in imposing their will in the gulf. Soviet and U.S. officials privately conceded that the joint condemnation of Iraq would do little to change the military situation in Kuwait, where Iraqi troops now appear to be firmly in control.

Questioned by reporters, Baker once again refused to rule out future U.S. military intervention in the gulf, saying that speculation served no useful purpose. In years past, Soviet officials would have attacked any suggestion that the United States was even considering such action in the Middle East. Shevardnadze, however, said merely that the Soviet Union had no plans to intervene militarily in the region and he understood that this was also the U.S. position.

Both ministers warned of "very serious consequences" if Iraq failed to ensure the security of U.S. and Soviet citizens in the region. According to Shevardnadze, there are between 7,000 and 8,000 Soviet citizens in Iraq, including many military advisers, and 900 in Kuwait. U.S. officials said that about 3,800 Americans are now in Kuwait.

Shevardnadze said Iraq had not replied to Thursday's formal Soviet statement calling for the withdrawal of the invading force and the restoration of Kuwait's territorial integrity. But he said Iraqi officials in Baghdad had assured the Soviet Embassy there that Iraqi troops would be pulled out of Kuwait "very soon."

The Iraqis invaded Kuwait despite private U.S. warnings at "high levels," a senior State Department official traveling with Baker said after the press conference. "We had communications with them," the official said, and "there was a general warning, yes. . . . We communicated at several different levels, including high levels."

The official said the United States first proposed the joint Soviet-U.S. statement. "We raised it with them. They liked the idea right away," he said, "although they had some hesitation" given their treaty of friendship with Iraq and longstanding good relations. But that "was not something in the end that was going to prevent them from going along with this," the official said.

Asked whether there was any discussion between Washington and Moscow of the possibility of joint military action against Iraq, the official said, "there was none." But he said the joint call for an arms cutoff should be seen as a "springboard to additional action, particularly if there is no response from the Iraqis."

An arms cutoff was an especially significant action against Iraq, the U.S. official said, because "you have a regime that has a huge appetite for weapons." Cutting off arms means "you're hitting this regime where it lives and that's a very good starting point. Does it mean that we won't go beyond? No."

The official said there were no indications "that I am aware of" that Soviet military advisers in Iraq played any role in the planning or execution of the invasion. "The Soviets have not said whether they intend to withdraw their advisers," he said.

The official said Iraq's major arms suppliers are the Soviets, "the French rank a close second" and others include China, Brazil and possibly South Africa. "I am not certain whether there has been a discussion at this point" with China about cutting off arms to Iraq, he said. "But I am certain that there will be such a discussion."

The joint statement said that the United States and the Soviet Union believe the international community should not only condemn the Iraqi invasion of Kuwait but also take "practical steps in response." It called on Arab states and the Nonaligned Movement to ensure that U.N. Security Council resolutions demanding the withdrawal of Iraqi troops are fully implemented.

"The Soviet Union and the United States are now resorting to an unusual step: They are jointly urging the entire international community to join them and suspend all supplies of arms to Iraq on an international scale," the statement said.

The Iraqi invasion of Kuwait has already sparked an unusual debate here over the Soviet Union's unquestioning support for Saddam in the past. One Soviet specialist on the Arab world, Igor Belyayev, described the Iraqi army as "a monster we have ourselves created."

Writing in the Communist Party youth newspaper Komsomolskaya Pravda, commentator Alexander Shumilin complained that the "basis of the might of the Iraqi army is military hardware that has been supplied to Iraq for years from the Soviet Union." He accused the Baghdad regime of attempting to solve its financial crisis at the expense of its small neighbor.

Such criticism of a key Soviet ally was virtually inconceivable until very recently. Over the past few months, however, Soviet academics and journalists have increasingly challenged the policy of channeling huge amounts of economic and military assistance to Third World dictators such as Saddam and Cuba's Fidel Castro.

Shevardnadze told reporters today that the Soviet leadership had been taken by surprise by the Iraqi move into Kuwait. He said that, at the time of his meeting with Baker in the Siberian city of Irkutsk just before the invasion, he had been "almost sure" the Iraqis would not attack Kuwait.