Amid the crisis over Iraq's invasion of Kuwait, Saudi Arabia has overcome its longstanding objection to diplomatic ties with the Soviet Union and is preparing to send its foreign minister to Moscow to negotiate a formal exchange of ambassadors, sources said yesterday.

But in these final high-level talks, the Saudi minister is expected to seek assurance that Moscow would not oppose a military offensive led by the United States and Saudi Arabia to push Iraq out of Kuwait if the U.N. trade embargo proves ineffective, the sources said.

Although the thaw between Moscow and Riyadh has been under way for three years, the final step toward formal recognition would occur as Saudi officials are seeking to strengthen international and superpower support for the embargo and possible future military action against Iraq.

Increasingly in recent days, U.S. officials and other sources who have met with members of the Saudi royal family have reported a strong resolve to move toward a military option against Iraq after an interim period of trade sanctions and completion of the U.S. military buildup in mid- to late October.

The Saudi ambassador to Washington, Prince Bandar bin Sultan, has informed key Arab ambassadors here of his government's plan to restore diplomatic ties with Moscow, the sources said, after five decades of estrangement wrought by official revulsion by the conservative Islamic monarchy to communism and atheism there.

The decision follows Saudi Arabia's announcement July 22 that it had established diplomatic relations with China. One source said recognizing Peking before Moscow was in part a reward to China for secret sales to Saudi Arabia in 1988 of CSS-2 medium-range ballistic missiles, which gave the Saudis a regional strike weapon for the first time as a deterrent against attack.

Exactly a month later, Bandar flew to Moscow for discussions with Soviet Foreign Minister Eduard Shevardnadze and later told reporters, "We greatly appreciate the Soviet position at the U.N. -- the condemnation of brazen aggression and the Soviet Union's insistence that Iraqi troops be withdrawn from Kuwait and that the country's legal government be restored."

The Soviet news agency, Tass, later said Bandar's visit had included talks on upgrading Saudi-Soviet relations.

Neither the Soviets nor Saudis has announced the pending arrival in Moscow of Saudi Foreign Minister Prince Saud Faisal, but the sources said he is to explore Moscow's attitude toward the prospect that Saudi Arabian, U.S. and other multinational troops might have to undertake offensive operations against Iraqi forces.

"The Saudis want to preserve the military option with the United States and other countries that want to go along," one source said, "and, if there is military action, they want to make sure the Soviets are on board, not playing games."

The Saudis do not expect the Soviets to participate in a military operation against Iraq, the sources said, but are concerned that, if the embargo fails to dislodge Iraqi President Saddam Hussein from Kuwait, a military offensive led by U.S. and Saudi forces must be preserved as an option that the Soviets would not block.

The Saudis have been pleased with Soviet support for U.N. resolutions condemning Iraq's invasion, calling for a worldwide embargo against Iraq and allowing multinational forces to erect a naval blockade to enforce the embargo. But Moscow has rejected Saudi suggestions that the Soviet Union should contribute naval or ground forces to defend Persian Gulf states.

Much of the Saudi-Soviet negotiations have been conducted here between Bandar and Soviet Ambassador Alexandr Bessmyrtnykh, sources said. The initial report that a final timetable for reestablishing ties was under discussion appeared last week in the Los Angeles Times, which said no timetable had been set.

But Faisal's mission to Moscow suggests that, if the Saudis obtain assurances being sought there, formal diplomatic relations could follow immediately, one source said.

A Soviet Embassy official said yesterday that Bessmyrtnykh is in Moscow,but that "bilateral discussions" with the Saudis have been ongoing. "The Saudi side is very sensitive," the official said. "They do not want any premature leaks."