The Soviet Union turned down a chance to influence Belgium's decision to deploy nuclear missiles by insisting on linking U.S.-Soviet negotiations on medium-range missiles to talks on space weapons, Belgian Prime Minister Wilfried Martens said today.

Martens' formal announcement to parliament that installation of the first 16 cruise missiles would begin this month, decided at a Cabinet meeting last night, was welcomed with warm applause from his parliamentary majority and jeers from members of the Flemish bloc of the opposition Socialists.

The Soviets' position, Martens indicated, makes it likely that negotiations that began this week in Geneva will be long and difficult, and "in these circumstances, there is no more reason to delay deployment."

Martens said that Belgian Foreign Minister Leo Tindemans, while in Moscow this week for the funeral of Konstantin Chernenko, asked Foreign Minister Andrei Gromyko if the Soviet Union might drop its insistence that progress in the Geneva talks on intermediate- and long-range nuclear weapons be linked to negotiations on space weapons.

"If the U.S.S.R. had been able to accept a separate accord on medium-range weapons including the cruise , Belgium would have put off the deployment of the first nuclear missiles until the end of the first session of the negotiations in order to give them the best chance of success," Martens said. The Soviet response to Tindemans, however, was that decoupling of the negotiations was "impossible," he said.

Belgian antimissile groups, which had planned a demonstration in Brussels Sunday, said the government's decision would not halt their efforts. "The decision has come, but this does not mean that the opposition to the missiles will cease," said the General Federation of Belgian Workers, a socialist union.

Belgian officials said that the missiles might arrive at the Florennes air base, 45 miles south of Brussels, in U.S. military transport planes within the next few days. U.S. officials declined to say exactly when the weapons would be flown in.

Leaders of Marten's Flemish-based Christian People's Party had called on Martens last November to delay deployment to give the revived U.S.-Soviet arms talks a chance to succeed and to defuse antimissile sentiment in Belgium.

Before visiting Washington in January, Martens said that he was not going to the United States to "negotiate" the missile deployment, which was a collective NATO decision made in 1979. When he returned to Brussels he said Tindemans would consult with other NATO nations to decide on an installation timetable.

The replies from the NATO nations, Belgian officials said, were clear: Belgium must begin deployment on schedule to demonstrate alliance solidarity as the new arms talks began. The move for deployment also was strengthened by the U.S. announcement last Monday that the Soviet Union had increased its number of operational SS20 intermediate-range missiles, officials said.

The government, in making its decision, made one gesture to opponents of the missiles. Martens told parliament that if there is no U.S.-Soviet accord to limit arms negotiations by the end of 1987 and talks are no longer under way, Belgium will deploy the remaining 32 cruise missiles it is to receive under NATO plans. If the talks are still in progress, the government will wait a maximum of another six months before installing the missiles.

In the first Soviet comment on the Belgian move, the news agency Tass said that the action had been taken "contrary to protests by an overwhelming majority of the Belgian population," Reuter reported from Moscow. Tass also said that the decision to deploy raises "additional obstacles" to the new arms talks in Geneva, which are in recess until Tuesday.

Tass said that the Belgian government's decision came "at a time when on the international horizon, there appeared sparkles of hope for a relaxation of international tension," United Press International reported.

Lord Carrington, the NATO secretary general, welcomed the Belgian decision to deploy. "Experience over the years has shown that the Soviet Union doesn't get down to business if it thinks that concessions are going to fall into its lap without it making any concessions on its side," he said.