The Warsaw Pact alliance described U.S.-Soviet summit conference as "useful" and "highly important" tonight following a meeting between Soviet leader Mikhail Gorbachev and six Eastern European Communist chiefs in Prague.

In a communique issued by the Soviet news agency Tass and East European news services, Gorbachev and the leaders of Moscow's six European allies said the summit "created more favorable conditions for improving the international situation and returning to detente."

The statement said that although the Geneva meetings "could not solve the concrete problems of arms control and reduction, it is highly important that the meeting has confirmed that ways must be sought to end the arms race and prevent the spread of arms to outer space."

Gorbachev, the report said, gave "detailed information" about the summit and was praised by the alliance leaders for his "constructive attitude" and "extremely important contributions." It added that "the talks were direct and open, the talks were necessary, and the results were useful."

The Soviet Bloc meeting was the second held by Gorbachev with his allies to discuss the summit and appeared to reflect the Soviet leader's interest in creating closer cooperation within the Warsaw Pact while matching President Reagan's consultation with NATO allies, diplomats and other observers said.

The communique declared that Gorbachev's positions in Geneva were "the substantiation of the peace-loving attitude elaborated jointly by the socialist countries" at their presummit meeting in Sofia, Bulgaria. In an apparent signal of intrabloc relations after the summit, the communique stressed the "primary importance attached to unity and cohesion of the allied socialist countries" and "broadening cooperation and joint stands in all areas . . . amid complicated international conditions."

The joint statement said that the summit had "created a basis for dialogue aimed at achieving change for better both in Soviet-American relations and generally in the world," and added that the Warsaw Pact countries would "stand up together and continue to do their best in the future in order to achieve a change for the better in European and international affairs."

Gorbachev flew to Prague from Geneva at midday and was joined in the Prague Castle by Gustav Husak of Czechoslovakia, Erich Honecker of East Germany, Wojciech Jaruzelski of Poland, Todor Zhivkov of Bulgaria, Janos Kadar of Hungary and Nicolae Ceausescu of Romania. Each of the Communist Party leaders was accompanied by his government's foreign minister.

In contrast to both the Sofia meeting and the Soviets' propaganda campaign before the summit, today's session was shrouded in official reserve. No official announcement of the gathering was made until Gorbachev had arrived in Prague, and observers said Radio Prague did not report the arrival of other East European leaders.

Western diplomats in Prague, contacted by telephone, said the meeting was believed to have lasted for about an hour, and Gorbachev and the other leaders later dined at the castle, a spectacular baroque palace on a hill overlooking the city. The leaders were expected to leave Prague tonight.

Before the alliance talks, Gorbachev met separately with Czechoslovak leader Husak, one of Moscow's strongest supporters.

A statement issued afterward said that the two leaders agreed that the results of the Geneva summit "makes progress possible toward such mutually acceptable agreements that, based on the principles of equality, would prevent the spread of the arms race to the outer space and would make the reduction of arms possible on Earth."