MOSCOW -- Eduard Shevardnadze emerged in the past year as the most important and innovative diplomat on the world scene. His shock resignation as Soviet foreign minister imperils not only the course of U.S.-Soviet relations but also the effort to create an effective new world order out of superpower cooperation.

It is not diplomatic failure abroad but an intense domestic power struggle at home that accounts for Shevardnadze's bolt from the blue. Equally important is Soviet President Mikhail Gorbachev's failure to back his Georgian ally forthrightly on the Persian Gulf crisis, which has become as much of a political football in the unruly Soviet parliament as it is in Washington.

Opponents looking for clubs to use against Gorbachev and Shevardnadze have seized on the foreign minister's strong support for American policy in the Gulf. From the left come complaints that Shevardnadze has not sufficiently consulted or explained the policy. From the military come expressions of nostalgia for the old policy of seeing Saddam Hussein as an impetuous but ultimately reasonable leader to do a deal. From ideologues there is an appeal to isolationism.

Sound familiar?

This mirror-imaging of the political situation in Washington on the Gulf is in one way the good news. It testifies to the openness of political struggle and debate here. But the bad news of Shevardnadze's departure from Gorbachev's side -- if it is not reversed in the coming days -- overshadows that silver lining.

"The Shevardnadze option" is how Soviet foreign policy analysts have come to describe his efforts to tie the country's future irrevocably to the West and particularly to the United States. The Soviet Union's survival depends on Western cooperation and is well worth abandoning ideological confrontation and Soviet support for Third World dictators, in this view.

It is Shevardnadze's version of preventing the Soviet Union from becoming a pitiful helpless giant in world affairs. To have influence abroad Moscow must now cooperate with Washington, as it is doing in the Persian Gulf and as it did earlier in setting the stage for German reunification.

Shevardnadze's role in inspiring and creating the diplomatic framework that produced German reunification has still not been fully divulged. But it is likely that he was the true father of the concept of the Two Plus Four negotiating formula on Germany. Shevardnadze also overcame opposition of Central Committee and military ideologues in getting Gorbachev to accept a united Germany in NATO.

He is now the point man in the same way on the Persian Gulf, resisting the argument of regional expert Yevgeny Primakov and others that the Soviets should keep enough distance from Washington to be able to broker a settlement with Iraq and to continue an active role in the Third World.

As he has in most of his domestic battles, Gorbachev has tried to bridge the two approaches. He emphasizes both his political support for the goals of the American-led coalition and his opposition to the use of force. The result has been to keep the Primakov option in play and to encourage domestic attacks on Shevardnadze's bold public support for Washington.

Primakov has been frequently mentioned as a likely successor to Shevardnadze. But he has earned the distrust of senior officials in the Bush administration, who feel he seeks to provide Saddam with a face-saving compromise at Kuwait's expense.

The White House would see a Primakov-for-Shevardnadze switch as a bad omen for U.S.-Soviet cooperation as the Jan. 15 Gulf deadline approaches and as the superpowers attempt to nail down a strategic arms reduction treaty for a February summit. Such a chance would also confirm the spreading impression that Gorbachev has reached a dead end in foreign policy as well as domestic affairs.

"Gorbachev now mixes tactics with strategy. He makes compromise his strategy, which leaves the Soviet Union without a clear role to play internationally," Alexei Arbatov, an influential defense analyst in the Soviet academic community and once an unqualified admirer of Gorbachev, said a few days before Shevardnadze's resignation.

"Such an approach means the Soviet Union will not be an active player in the new international order. The Soviet Union will be a passive recipient of whatever benefits there are in a new world order" run by the United States, added Arbatov, who believes the Soviet Union should have sent a symbolic military force to the Gulf.

"The initial stage of Gorbachev's foreign policy, of destroying ideological confrontation and fossilized thinking here, has been basically accomplished," says Andrei Kortonov, another leading Soviet foreign policy analyst. "Now we have to shift to a less emotional, more realistic diplomacy based on national interest. That requires you to choose, especially when you act from a position of weakness. There is a question whether Gorbachev will be able to make that shift."

Shevardnadze's departure ends the most innovative and positive phase in the history of Soviet foreign policy. We have come to think of it as the Gorbachev era, as the Nobel Prize Committee confirmed this year. Now we will learn if we should have been thinking of it as the Shevardnadze era all along.