MOSCOW, JUNE 12 -- Soviet President Mikhail Gorbachev said today that he could accept a unified Germany as a member of NATO as long as any military force in what is now East Germany maintains what he called an "associate membership" in the Warsaw Pact. Western leaders immediately rejected the suggestion.

Gorbachev's complicated proposal envisages a "transition period" for a unified Germany, during which troops in what is now West Germany would be under NATO command while troops in the east would be under control of the German government but would have "associate" status in the Warsaw Pact.

"Our position is the following: We would agree on {German} entry into NATO, if the West accepts associate participation," Gorbachev said. In describing his proposal, the Soviet president used the phrase "dual membership," but it was clear that NATO's role in a unified Germany would be stronger than that played by the Warsaw Pact.

Gorbachev said the troops in the eastern region could include Soviet units, but he was vague about the definition of associate membership. He also urged that the Western and Eastern military alliances agree to an eventual transformation into a united all-European security system.

The Western allies, with West German Chancellor Helmut Kohl in the forefront, promptly dismissed Gorbachev's suggestion, correspondent Edward Cody reported from Bonn. "This is a proposal we do not consider realistic," Kohl told reporters in the West German capital.

The Western response to the proposal, which Gorbachev said he put to President Bush in Washington last week, seemed designed to rule out any further consideration of the idea and to focus attention instead on avenues that West Germany, the United States and other NATO allies feel are more worthy of exploration.

{"The matter was discussed here," President Bush said at a White House photo session. "Our position is well known to him, which is that a unified Germany should be in NATO with no conditions."}

The Soviet leadership's subtle shift on the issue of German military alliances is yet another move in the diplomatic struggle over the shape of post-Cold War Europe and its longstanding security pacts. Gorbachev previously had ruled out membership of a unified Germany solely in NATO, and at one point he even proposed, to the dismay of Western leaders, that Germany be a full member of both the North Atlantic Treaty Organization and the Warsaw Pact.

Gorbachev, reporting to the Soviet legislature on his recent meetings in Washington, praised Bush for showing understanding and restraint regarding the Soviet Union's domestic problems. He said he told Bush, "We will agree on entry of Germany into NATO only if you accept associate participation . . . and only if there is a simultaneous process of coming together of the two blocs."

With the countries of Eastern Europe electing independent, non-Communist governments and seeking less rigid relations with Moscow, the Warsaw Pact has weakened dramatically in the past half year. The Soviet Union has found itself adjusting its stand on the German question several times, dealing, it appears, from a position of diplomatic weakness.

Gorbachev, however, warned today that "if we have the feeling we are not being taken into account on the German issue, then the positive processes in Europe will be under serious threat. This is no bluff."

Gorbachev said that both the Soviet Union and the United States should have the option of pulling out of any new security arrangement if one side feels the spirit of the agreement is being violated. He said he hoped that a new security agreement regarding a unified Germany would be a "linking element or forerunner" to a comprehensive European security structure in the future.

Gorbachev said that if leaders of the 16 NATO nations decide during their summit in London July 5 and 6 to transform NATO into a less military, more political alliance, then the problems of alliances and a unified Germany would be a great deal easier to solve. He said that if his German formula were adopted, "then this 'double' membership could be the outline for new European structures."

Answering a question from the floor of the legislature, Gorbachev rejected the suggestion that a unified Germany should have a status in NATO similar to that of France, which holds a political, but nonmilitary position in the alliance. "That's a myth," Gorbachev said. "Their armed forces are taken into account by NATO." He called for troop cuts throughout Germany, in both the west and east.

Gorbachev told the legislators that the Western position had grown more flexible in recent weeks and said he was encouraged by the responses of both Bush and British Prime Minister Margaret Thatcher to his proposals.

He said he would not insist that the Soviet plan become the final word on Germany and new security alliances. "We don't have any claims to have our version put in place," Gorbachev said. "Let it be anyone's -- Mrs. Thatcher's or anyone's -- so long as it corresponds to our common interests."

{On Capitol Hill, meanwhile, Secretary of State James A. Baker III, told the Senate Foreign Relations Committee that it is "premature" for him to express a view on possible shifts in NATO's nuclear policies, including the question of whether a "no first-use" policy on nuclear weapons ought to be adopted. Responding to Sen. Joseph Biden (D-Del.), who advocated a new NATO policy under which nuclear weapons would be used solely to deter nuclear attack, Baker said that this and many other issues of NATO military strategy are likely to be considered at the NATO London summit.}Correspondent Cody added from Bonn:

Despite Chancellor Kohl's rejection of the associate membership suggestion, a West German official said that Foreign Minister Hans-Dietrich Genscher made clear progress Monday in prolonged talks on reunification with his Soviet counterpart, Eduard Shevardnadze, in the Byelorussian city of Brest.

Their conversations centered on possible changes in NATO strategy and military doctrine that would make the Western alliance into a more political grouping and perhaps open the way for some kind of cooperation with the Warsaw Pact, the Foreign Ministry official said.

In what was seen as an effort to keep up momentum in Genscher's separate talks with Shevardnadze, the West German Foreign Ministry declined public comment on Gorbachev's proposal for associate membership in the Warsaw Pact.

At NATO headquarters in Brussels, the alliance as a whole also rejected Gorbachev's suggestion of associate membership. Apparently referring to the possibility of cooperation between the two alliances, however, a NATO spokesman described some of Gorbachev's ideas as "interesting" and said his declarations in Moscow would be studied closely. This was regarded as a deliberate softening compared to previous NATO rejections of Soviet proposals concerning a reunified Germany.

Prime Minister Thatcher, who returned Sunday from a four-day visit to the Soviet Union, said in London that the idea of one country belonging to two alliances seemed doubtful and that Germany must retain its full membership in NATO. But the British leader also emphasized that NATO must take Soviet security concerns into account as Germany reunifies.

Staff writer Don Oberdorfer contributed to this report from Washington.