MOSCOW, NOV. 4 -- Soviet leader Mikhail Gorbachev, signaling new flexibility in Moscow's dealings with Eastern Europe, indicated today that the Soviet Union would encourage approaches to communism that exploit "all the diversity of experience."

In a speech to foreign delegates attending celebrations marking the 70th anniversary of the Bolshevik Revolution, Gorbachev appeared to break ranks with previous Soviet leaders who usually have insisted upon rigid conformity by Eastern Bloc allies with the Kremlin's views.

Gorbachev rejected what he called the "arrogance of omniscience {that} speaks of a tenacious habit of rejecting other points of view out of hand."

In another development that could have a profound impact on Soviet allies, the director of the Soviet Communist Party's leading ideological think tank said today it may be time for a new analysis of the 1968 "Prague spring" that led to the Soviet invasion of Czechoslovakia.

"I think there is a need to think over the events of 1968, the intervention," said Georgi Smirnov, director of the Institute of Marxism-Leninism, at a press conference here.

Smirnov answered a question about a review of Czechoslovakia's 1968 move toward democracy by saying that it was a legitimate question that needed "a new assessment."

But he declined to give his own views on the period of liberalization in Czechoslovakia and the Soviet reaction to it. "I would not take this political and scientifically historic issue upon myself," he said. "I have a balanced attitude, but I cannot share it with you."

Gorbachev, in his comments today, also said: "Our perestroika with all its international effects is eliminating fear of a 'Soviet threat,' with militarism losing its political vindication." Perestroika, or restructuring, is Gorbachev's multifaceted program to overhaul the Soviet economy and society.

"No one has ready-to-use prescriptions," he said. "We are engaged in a search ourselves, and invite others to look jointly for the ways along which humanity could cross the mine field of our times and emerge in the 21st century, in a nuclear-free and nonviolent world."

Smirnov's brief comment was an indication that the exploration of sensitive subjects in Soviet history will go forward from the groundwork laid in Gorbachev's speech Monday.

That speech was seen as a compromise on several key historical topics, including the Stalin era. But several Soviet historians insisted at today's press conference that it was not meant as the last word on the intrepretation of history. "It gives us a very broad possibility for creative work and study," Smirnov said.

Gorbachev referred to the historical section of his speech when he said that the Soviet Union has "once and for all overcome the attempts at trifling with history when, at times, we believed what we wanted to believe rather than what was."

Other signs today indicated that the campaign for a review of traditional Soviet approaches to history is continuing unabated. In an interview that appeared today in the weekly Moscow News, Andrei Sakharov, the physicist and human rights activist who less than a year ago was living in internal exile, pressed for full disclosure of the facts surrounding the Cuban misssile crisis of 1962.

Sakharov's statement, the most extensive by the former dissident leader to appear in the Soviet press, was made in reaction to the film "Risk" that appeared on Soviet television last week, offering a positive portrayal of Soviet leader Nikita Khrushchev, a nonperson here since 1964.

Sakharov, praising Khrushchev as an "outstanding world leader," was critical of the film's lopsided approach to the U.S.-Soviet standoff over Cuba 25 years ago. "It was not mentioned that it began with the placement of our rockets on Cuba," Sakharov said.

The same issue of Moscow News, considered the flagship of Gorbachev's policy of glasnost, or openness, also carried a harsh attack on the late leader Leonid Brezhnev, whose 20-year rule until his death in 1984 is now being blamed for the stagnation and failures of Soviet domestic and foreign policy.

The article, written by Soviet author Daniel Granin, said Brezhnev basked in the adulation of toadying underlings. "Servile spirits insisted a great country must have a great leader, and they began to manufacture one . . . . historians should seek to analyze in detail the mechanism of that sad process."

The statement by Smirnov, made at a press conference to discuss the historical implications of Gorbachev's speech, was seen by some observers as falling within the context of criticism of the Brezhnev era. Smirnov, a candidate member of the Central Committee, was named to head the influential, and traditionally highly conservative, institute early this year, when the debate over history was beginning in the Soviet press.

Although information about it was tightly controlled here, the 1968 invasion of Czechoslovakia had a reverberating effect within the Soviet Union. Moscow's brutal reaction to the Czechs' experiment with democracy caused disillusionment among Soviet intellectuals and spurred the growth of the dissident movement.

Some observers have compared the opening of Soviet society and debate under Gorbachev to the freedoms enjoyed in Czechoslovakia in the spring of 1968. But the comparison is ill-suited because here, unlike Prague, the party is in firm control of the reform process.

Several analysts here also noted that a reappraisal of Soviet reaction to the reforms initiated by Alexander Dubcek would be unsettling for the current regime in Prague.

Still, by even raising the possibility of a review of the causes and consequences of the 1968 events, Smirnov suggested that the review of history may turn into a review of recent foreign policy, particularly of decisions made during the Brezhnev era.

Smirnov said today his institute played little role in crafting Gorbachev's speech on Monday.

In a brief interview after the press conference, he said Gorbachev had been advised on the history section by a small group of people, but that he was not among them.