Soviet Foreign Minister Andrei Gromyko warned the West tonight that a NATO decision next month to station U.S.-built missles in Western Europe would "destroy" a Soviet proposal for immediate negotiations to limit such weapons.

Gromyko's remarks, coming in a rare public press conference after two days of talks with West German leaders, are bing viewed as an escalation of Moscow's pressure on West European countries not to allow deployment of U.S. medium-range, nuclear-tipped Pershing II and Tomahawk cruise missles on their soil.

Since there is as yet no specific forum for negotiations on such tactical weapons, the precise implications of Gromyko's remarks were not clear.

Gromyko's words, however, seemed to go beyond earlier warnings of Soviet President Leonid Brezhnev, who has said the NATO decision would "undermine" future arms control negotiations.

On Oct. 6, Brezhnev announced in East Berlin that the Soviets were willing to discuss limitations in these medium-range weapons but only if NATO refrained from deploying any of them.

The Western alliance has already made clear in preliminary meetings, however, that it will go ahead now with production and, beginning in 1983, with deployment of the weapons to balance new Soviet missiles and bombers already in place and targeted on Western Europe.

The official NATO decision is expected three weeks from now at a meeting in Brussels. The expected arms modernization plan is to be accompanied by a NATO arms control proposal meant as a response to the Brezhnev initiative on arms limitations.

Tonight, Gromyko seemed to be ruling out such a NATO proposal as a basis for future negotiations if indeed it is accompanied by the weapons modernization plan.

If NATO "should come to such a decision, if our proposals for immediate negotiations should be rejected, the basis for negotiation would be destroyed. It would not exist," he said.

"When we say we must begin negotiation immediately," the Soviet foreign minister said, "we meant it must begin without a decision having been made on production and stationing" of the new weapons.

The Western view is that the new missiles are needed not only to balance the Soviet weapons but also to allow the West to negotiate from a stronger position, since there is little the West can now bargain with in an effort to get the Soviets to reduce their existing force of new SS20 multiple-warhead intermediate-range missiles.

Gromyko said such an approach would aggravate the political situation and start a new spiral in the arms race. He said the SS20s were not new weapons but rather "only undergoing a certain moderization" that was started five years ago.

The expected NATO arms control proposed envisions bringing these various weapons into the next round of strategic arms limitation talks, or SALT III, assuming that SALT II now before the Senate is ratified. The next round would focus on various shorter-range weapons that thus far have fallen outside the category of ocean-spanning missiles and bombers included in the initial SALT discussions.

Thus, while Gromyko did not specifically say there would be no basis for SALT III if NATO decides on new arms, he seemed to reject NATO use of SALT III as the vehicle for its arms control proposal.

Gromyko emphasized that SALT II had taken some seven or eight years to negotiate and still was not ratified and that SALT III might include a great variety of even more complicated weapons questions. His point was that SALT was a drawn-out process and he repeatedly stressed the Soviet demand for immediate negotiations based on Brezhnev's initial opening and what Gromyko described as a present condition of nuclear balance in Europe.

Gromyko said the idea of stationing new missiles on U.S. bases in Western Europe, from which they could reach the Soviet Union, would violate the principle of equality established by Brezhnev and President Carter at the SALT II signing in Vienna this summer. The new Soviet rockets are unable to reach the United States but can strike all NATO targets in Europe.

Gromyko's apparent raising of the stakes here tonight came as a surprise because it was already clear that NATO intends to go ahead with its plans and communist diplomats say privately that Moscow is reconciled to that.

The Soviet foreign minister acknowledged tonight -- after four hours of private meetings with Chancellor Helmut Schmidt -- that he did not get very far with West Germany on this issue.

"We note with regret that the Federal Republic, as far as can be determined from today's discussions, has taken a position" supporting the NATO dual-approach plan, Gromyko said.

His press conference remarks come just 10 days before a key political convention of Schmidt's Social Democratic Party and while the Dutch government is still undecided about going along with the NATO plan that involves basing the new weapons in West Germany, Britain, Italy, Belgium and Holland.

The prospect of negotiations that could limit the deployment of new weapons is a major factor in the Western strategy to bring long reluctant countries such as Holland. Thus, Gromyko's remarks tonight suggesting that there would be no basis for negotiations could still prove important. CAPTION: Picture, ANDREI GROMYKO . . . says weapons talks jeopardizedd