Soviet leader Mikhail Gorbachev has threatened Saddam Hussein, saying that if he doesn't pull out of Kuwait, he will be looking down the barrels of Soviet guns.

High-level U.S. intelligence sources told us that Gorbachev's secret ultimatum was delivered by a special envoy Yevgeny Primakov on Oct. 5, when he met with Saddam in a visit billed as a discussion about Soviet citizens trapped in Iraq.

Primakov, 61, is a confidant of Gorbachev's and an economist. He held a news conference after the meeting with Saddam and reported, "I am not pessimistic any longer toward the prospects of a political solution for the crisis."

What he didn't reveal was why he was no longer pessimistic. He had threatened Saddam with Soviet military might, and Saddam was visibly surprised.

U.S. officials with access to highly classified intelligence reports say that Primakov issued Saddam an "ultimatum" that was "unequivocal." If he didn't leave Kuwait, "he could expect war with the Soviet Union," according to our sources.

The usually unflappable Saddam was taken aback. He had no immediate response except to soften his rhetoric about staying in Kuwait. It didn't take him long to regain his composure and threaten the Soviets in return. On Oct. 12, the official Iraqi news agency quoted a military spokesman warning the Soviets that if they shared any Iraqi military intelligence with the United States, Iraq would hold Soviet citizens hostage.

"We warn them against such behavior if it happens," the spokesman said. "If the Soviet Union gave the United States the information it was seeking, we would be forced, unfortunately, to act in a way that protects our national security. Among those measures would be to halt the departure of Soviet nationals."

We recently reported that the Soviets have already begun to leak intelligence to the United States about Iraqi weapons capability. We also revealed that the Soviets are soon expected to provide even more vital intelligence on the performance of Iraqi soldiers and weapons during the long Iran-Iraq war and profiles of Iraqi military advisers.

With that information passing from the Soviets to the United States, Saddam will soon have to decide whether to follow through with his threat to hold Soviet hostages. Our sources estimate that there are about 5,000 Soviets in Iraq.

If Saddam makes them his unwilling "guests," our intelligence sources say, it is likely that Gorbachev will follow through with his ultimatum and send Soviet soldiers to join U.S. troops in Saudi Arabia.

There is a hint that the Kremlin is still banking on Gorbachev's ultimatum. On Oct. 14, the Soviet news agency Novosti reported that Saddam may be willing to get out of Kuwait in exchange for some strategic land. Novosti also said that Primakov had warned Saddam that Gorbachev would not stand in the way of a U.S. military action.

The official Iraqi response to the Novosti report was that "Kuwait was and will continue to be Iraqi land forever."