While West Germany's new conservative government and other West European countries cling to hopes for early progress in Soviet-American arms-control talks as a way to defuse growing political tensions on the continent, U.S. negotiators now say chances for such a breakthrough appear bleak.

Eugene Rostow, director of the Arms Control and Disarmament Agency, told a press conference in Brussels this week that he did not expect any movement in the Geneva negotiations on European-based nuclear weapons "until five minutes before deployment" of the North Atlantic Treaty Organization's 572 new cruise and Pershing II missiles.

Facing the prospect of elections next March, Chancellor Helmut Kohl and his center-right coalition in Bonn have been eager to cite some grounds for optimism in the stalled talks to thwart a powerful tide of antinuclear sentiment in West Germany and other European NATO countries.

Rostow's pessimistic appraisal, however, seems likely to intensify concern in Bonn that the deployment plan will become a prime electoral issue in what West German analysts already label "the year of the missiles."

Under NATO's current strategy, Britain, West Germany, Belgium, Italy and the Netherlands are scheduled to begin deployment of the modern cruise and Pershing nuclear missiles in December 1983 unless the arms-control negotiations bear fruit. The United States seeks removal of 600 Soviet intermediate-range missiles capable of hitting Western Europe.

Rostow, who is making a tour of the five nations' capitals to consult on deployment plans, said he is advising the NATO allies to prepare calmly and not to expect a significant Soviet initiative until the last moment, according to wire services.

"We are alert to any Soviet hints or proposal of a possible outcome which might enhance alliance security and solidarity," Rostow said. But Moscow "has reiterated with some vehemence . . . that it could retain its potential for nuclear blackmail, namely that the U.S. could have no intermediate-range nuclear forces in Europe while the Soviet Union could keep its entire arsenal of such forces threatening Europe, and perhaps even enlarging it."

A State Department official says that even though NATO allies have endorsed the decision -- to plan deployment while seeking to negotiate a basis for not having to deploy -- political pressures to withhold the missiles are "expected to build and will become enormous" next year in Europe if disarmament groups revive antinuclear protests as the deployment date draws near.

Those pressures could begin to surge as early as January, when West Germany would open its two-month official election campaign if Kohl's plans for a March vote are carried out.

However, Kohl must secure agreement from the opposition Social Democratic Party to enact changes in the West German constitution to hold an early vote. National elections are not scheduled until 1984.

Even though NATO's plan to modernize its European nuclear arsenal was hatched by Kohl's Social Democratic predecessor, Helmut Schmidt, in 1977, some Christian Democrats are worried that their electoral fortunes may suffer by defending the deployment decision in their role as the governing party.

"Some Christian Democrats had grave misgivings about going into government because they did not want to be tarred as 'the missile party,' " says Lee Sigal, a Brookings Institute specialist in European politics and security matters who recently returned from West Germany.

A no-confidence vote toppled Schmidt on Oct. 1 and ushered in Kohl as chancellor after the Free Democrats switched allegiances and sided with the Christian Democrats.

The change in power in Bonn was quietly welcomed by the Reagan administration, which was irritated by Schmidt's arrogance and his tart disagreement with a range of U.S. foreign and economic policies.

A few Christian Democrats, however, are concerned that Washington may misconstrue Kohl's more compatible style as an indication that their party is less insistent on the need for rapid progress on arms control. "The CDU worries about the missiles and the political fallout are just as real as those felt by Schmidt's Social Democrats," says Sigal.

West German diplomats report a strong conviction among some political elements in their country that contends the Reagan administration is not really serious about reaching an accommodation with the Soviets over the European missile question.

If elections are not held next March and proceed as originally scheduled in 1984, the deployment question will grow even more critical as an emotional political issue. The Social Democrats are scheduled to hold a crucial party congress in late 1983 that could result in the party repudiating Schmidt and renouncing the NATO deployment in favor of an outright ban on the new missiles.

Schmidt has vowed to fight such a move, but some analysts believe that the missile controversy could become so inflamed just prior to the deployment date that his influence might not hold sway.

The Christian Democrats are deeply apprehensive that as the new party in power, the antinuclear groundswell could turn against them, especially if the Social Democrats reverse themselves on the missile issue next year.

If deployment takes place, the prospects for violent demonstrations at the missile sites already have made officials in Washington and Bonn uneasy about potential repercussions on NATO morale.

"Unless some miracle occurs in the negotiations, the political costs of deploying the missiles are going to be very high," predicts a West German diplomat. "Both major parties, Christian Democrats and Social Democrats, are going to suffer."

In the Netherlands, where Socialists gained the largest share of votes in September elections on a platform demanding a ban on new missiles, plans for a possible center-left coalition were scrapped as the Christian Democrats turned to the right-wing Liberals as a future governing partner that shares their position to proceed with deployment if the arms talks fail.

Other European countries slated to receive the cruise and Pershing II missiles do not anticipate much political disruption if deployment goes ahead.

In Italy, the governing center-left coalition has firmly endorsed the NATO strategy and begun preparations to install the missiles in a remote part of Sicily -- a factor that Italian officials admit has contributed to the subdued public reaction.

Another reason for the absence of antimissile protests, say Italian diplomats, is that the active role played in the disarmament campaign by West German and Dutch church groups has not been emulated by the Catholic Church in their country.

Belgium, which like the Netherlands is due to receive 48 of the new missiles, is expected to follow the NATO line -- barring an unexpected challenge to the center-right coalition between Christian Democrats and Liberals.

Britain, behind the staunchly anti-Soviet policy pursued by Prime Minister Margaret Thatcher, is also wedded to the NATO commitment.

The Tory government is expected to proceed with the first installment of the new missiles in December 1983, despite a vocal peace movement within the country and an opposition Labor Party that recently endorsed a call for unilateral disarmament.