Brussels — President Reagan's new flexibility in the intermediate-range missile talks has probably scored a propaganda coup that could undermine the antinuclear movement, many European leaders say.
Though no figures have been officially proposed, Mr. Reagan announced Wednesday the US would limit the number of missles deployed if the Soviets would dismantle some of their missles.
There is significant disquiet, however, about his call for a space-age antimissile defense system and his tough tone against the Kremlin. As this decisive year progresses, such moves could not only make relations with the Soviet Union extremely stormy, comment Western leaders here, but also accentuate a rift between the United States and the European members of the NATO alliance.
A first test of whether the American move away from the ''zero option'' in the Geneva nuclear talks will reassure Western public opinion comes Easter weekend, when peace and disarmament groups have plans to demonstrate in a number of countries and cities. The ''zero option'' would have the Soviets dismantle their medium-range missles aimed at Western Europe in exchange for NATO not deploying 572 cruise and Pershing II missiles.
Most press and other comments point out that the Soviet Union can be expected to maintain a tough negotiating stance in Geneva in the hopes that Western public opinion and the antinuclear movement will mount in opposition to cruise and Pershing II missiles, whose deployment is scheduled to begin in December. The next phase of nuclear opposition after this weekend will be in May, when a massive gathering is planned in Berlin.
Many West Europeans note that just as the public and even some political leaders grew disenchanted with the zero option, they will not be permanently satisfied with the new ''interim solution'' on arms reduction if the Soviets refuse to accept lower ceilings on intermediate-range arsenals.
Already leaders of peace groups opposed to the planned deployment of 572 American cruise and Pershing II missiles in several NATO countries have characterized the ''interim solution'' as unacceptable because it would mean the installation of some of those weapons.
Although government statements in London, Bonn, and Paris welcomed the American President's Wednesday announcement, it was noticed that Chancellor Helmut Kohl failed to renew the 1979 NATO pledge to accept deployment of Pershing II missiles in December if the US-Soviet talks did not result in an agreement.
He said only that ''the alliance would examine its armament needs in view of the results of the Geneva negotiations.'' This position is said to be edging closer to that espoused by the opposition Social Democrat leader Hans-Jochen Vogel in his unsuccessful bid to unseat Mr. Kohl in the March parliamentary elections.
Commenting on the prospects for negotiations and deployment, Dennis Healy, the deputy leader of the British Labour Party who is generally regarded as a moderate on nuclear issues, noted that cruise and Pershing ''deployment would be the best anti-US, anti-NATO weapon ever devised.'' The Labour Party, in preparing for an expected national election later this year that it is not favored to win, has adopted a platform of unilateral disarmament of the British atomic arsenal. The issue could be one of the focal points of the British election campaign, as it was in West Germany.
In the wake of recent Reagan speeches, Mr. Healy and other West Europeans have expressed major reservations about the shifts in American policy. On the new ''interim solution'' proposal, a number of press comments noted that the President's stress on limiting warheads rather than missiles and insisting on covering all Soviet missiles and not just those aimed at Western Europe could make the proposal harder for the Soviet Union to accept.
Others have been dismayed by the President's espousal of an antimissile defense in outer space and his reference to the Soviet Union as ''an empire of evil.'' They fear it is part of an all-out effort by the US to drive the Soviet Union to the brink of bankruptcy through a contest in military technology that Washington thinks the West can win.
They say the antimissile defense will soon be joined by proposals for other new weapons, as recommended by a presidential panel studying alternatives to the controversial MX missile system.