NEWS ANALYSIS : Soviets Turn Agreeable, Surprise U.S. Officials : Diplomacy: The tone of relations with Moscow is showing marked improvement.

“In the past, we often rejected your ideas just because they came from your side,” Soviet Foreign Minister Eduard A. Shevardnadze told Secretary of State James A. Baker III in Moscow last week, according to a U.S. official who was present. “Now we’ve realized that a lot of your ideas are good ideas, and we can accept them.”

Moscow’s foreign minister put that new principle into startling practice this week by agreeing, swiftly and stunningly, to a pair of U.S. proposals on German reunification and troop levels in Europe.

American officials were openly surprised by the concessions.

“There’s a lot of things that happened more quickly than certainly I would have thought,” President Bush said Wednesday with the pinch-me-to-see-if-it’s-real tone of someone who had just won the lottery.

Even more important than the Soviets’ specific concessions, officials said, the overall tone of U.S.-Soviet dealings seems to have taken a marked turn for the better.

“It is simply different dealing with them now,” said one official who accompanied Baker to Moscow. “As a Sovietologist, I have to say that it’s an amazing experience. . . . It’s just unbelievable.”

As recently as a few years ago, he said, Shevardnadze and other Soviet officials typically listened to U.S. proposals in stony silence and responded--if at all--with tough counterproposals, weeks later.

Now, another official said, “At the highest levels of the Soviet government, there’s a willingness to reach a solution. . . . They don’t see the United States as the enemy anymore.”

During Baker’s visit to Moscow, Soviet negotiators engaged in an unusual, impromptu negotiating session with U.S. officials to seek a breakthrough in the talks on reducing strategic nuclear weapons. The Soviet legislature accorded Baker an unprecedented invitation to testify publicly before its committee on international affairs. And the KGB, the once-feared Soviet secret police, proudly gave U.S. human rights officials a tour of its headquarters to show off its new “rule of law” program.

Still, the most striking moves were the two that Shevardnadze made on Tuesday at a military aviation conference in Ottawa--because they abruptly reversed positions that Soviet leaders had only recently proclaimed.

First, Shevardnadze accepted a U.S.-designed plan for unity talks between East and West Germany along with a conference of the Allies of World War II--only two weeks after Soviet President Mikhail S. Gorbachev first acknowledged that German reunification was inevitable.

Then, in an even greater surprise, the Soviet official agreed to a Bush plan that the superpowers reduce their troops in Central Europe to 195,000 each--while allowing the United States an additional 30,000 troops in southern and Western Europe. Last week, Gorbachev rejected the plan as unfair.

“I’m still trying to figure that one out,” a U.S. official confessed happily. “We never dreamed they would accept it this quickly.”

Administration officials involved in the U.S.-Soviet talks of the past week said there were good reasons for Gorbachev and Shevardnadze to move as they did.

On the German question, they said, Gorbachev wanted an orderly process that guaranteed Moscow some influence over the pace and shape of reunification--an issue of major public concern inside the Soviet Union, where memories of World War II remain vivid.

On troop levels, they said, Gorbachev apparently decided that it was more important to secure an East-West agreement on conventional armed forces than to haggle over numbers that appear unrealistic as the political pressure mounted for troop withdrawals on both sides.

“Floors, ceilings--that stuff doesn’t matter so much any more,” one Bush adviser noted. “What matters is arranging an orderly withdrawal of forces and a sense that things are under control.”

Ironically, several officials noted, the Bush Administration was probably willing to compromise on the issue of its demand for 30,000 extra U.S. troops in Europe; Baker even said publicly that he wasn’t “wedded to it.”

But negotiating the issue would have delayed agreement, and Gorbachev, facing escalating demands from his former allies in Eastern Europe for a complete Soviet withdrawal, apparently decided that an internationally accepted troop level of 195,000 was better than no fixed level at all.

The turnabout on troops, one senior U.S. official said, was only the most recent and vivid example of a recurring phenomenon: the Soviet leader frequently changes his minimum demand--his “bottom line”--when circumstances shift.

“The important thing about Gorbachev is that he has always had a moving bottom line,” the official said. “If you give him an escape hatch, he moves beyond where you think he would go.”

But the Soviet leader has still kept U.S. officials guessing, because his flexibility isn’t consistent, another official noted.

“It’s disorienting,” the official said. “On some things that should seem central to their security, they move surprisingly fast. . . . On others, like Afghanistan, they don’t.”

Still, the Bush Administration is trying to respond--and to encourage more Soviet flexibility--by being more aggressive in offering areas for agreement.

“Because they’re different, it makes us different,” one aide said. “There are times . . . when we have to move in their direction.”

At Baker’s meetings in Moscow last week, he noted, the United States volunteered several new formulas to solve longstanding arms control issues.

And the Administration deliberately designed its proposal for German reunification talks with an eye toward Gorbachev’s political needs, he said.

“It was developed because we knew Gorbachev had to have a handle on this process,” he said.

The U.S. desire to help Gorbachev has been heightened further in recent weeks, since conservatives in the ruling Soviet Communist Party have begun attacking their leader’s foreign policy. At last week’s meeting of the Communist Party Central Committee, for example, conservative member Yegor K. Ligachev criticized Gorbachev for failing to slow the process of German reunification.

“What Gorbachev needs is things he can point to” in Moscow’s domestic debates, one official said. “He needs to show that he’s not the only one making concessions.”

Another official said the increased criticism “definitely seemed to affect Shevardnadze” in his talks with Baker. “It is increasingly important that they be able to explain their policy at home,” the official said.

As a result, some U.S. officials cringed when Bush proclaimed two weeks ago that Gorbachev was “the best Soviet leader” from the standpoint of American interests.

“Please tell your President that we don’t need that kind of support,” a Soviet liberal told U.S. diplomats. “That won’t help.”