MOSCOW, FEB. 6 -- President Mikhail Gorbachev called on Soviet citizens tonight to vote in favor of the preservation of the Soviet Union in an unprecedented referendum next month, suggesting that the future of a great world power lay in the balance.

Gorbachev used a 12-minute appearance on nationwide television to launch a full-blown political campaign to preserve the integrity of the world's largest nation on his terms. He sharply attacked Baltic leaders for attempting to upstage the Soviet Union's first nationwide referendum by holding their own polls on independence.

"The Soviet Union, not without reason, is called a superpower. Its policies have an influence on all the processes that happen in the world. Huge efforts have gone into acquiring such influence. But it can all be squandered very quickly," said Gorbachev, speaking from his Kremlin office, flanked by a red Soviet flag.

Gorbachev regards the March 17 referendum set for all 15 republics as a key element in a political strategy that is aimed at preventing the Soviet Union from falling apart and keeping his perestroika reforms alive. By casting himself as the guardian of a vast state made up of more than 100 distinct national groups, he is apparently hoping to mobilize public opinion and strengthen his political position.

The referendum has been worded carefully to appeal to as broad a section of the population as possible. Voters will be asked to answer "yes" or "no" to the following question: "Do you consider it necessary to preserve the Union of Soviet Socialist Republics as a renewed federation of equal Soviet republics, in which the rights and freedoms of people of any nationality will be fully guaranteed?"

A senior Communist Party official responsible for nationalities issues, Andrei Girenko, said today that public opinion surveys suggested that turnout will be around 80 percent and that three-quarters of those taking part in the referendum will vote "yes." In tonight's television statement, Gorbachev said it already was possible to say "in all certitude that Soviet people are for the preservation of the union."

At least four republics -- Lithuania, Estonia, Georgia and Armenia -- already have declared that they have no intention of taking part in the Soviet referendum. The two largest republics, Russia and the Ukraine, have agreed in principle to participate but reserved the right to add their own supplementary questions.

Describing the mere holding of a referendum as a "huge achievement of perestroika," Gorbachev called on the Soviet legislature to do everything to allow every Soviet citizen "to express his will about the future of our union." Aides have suggested that he might use his extraordinary presidential powers to ensure that the referendum is held throughout the Soviet Union on March 17, whether or not all republics agree.

Another possibility is that the Kremlin will encourage a series of small revolts against the pro-independence parliaments of the Baltic states by regions inhabited by large numbers of Russian speakers. Under a restrictive secession law adopted by the Soviet legislature last year, individual regions have the right to vote to remain part of the Soviet Union even if their republic decides to secede.

Such a step could play havoc with the territorial integrity of Estonia, Latvia and Georgia. In Lithuania, the population is much more homogenous but there, too, are some areas where Lithuanians are not a majority.

Gorbachev today accused Lithuania and Estonia of looking for flimsy pretexts to avoid the referendum. The Lithuanian parliament has ordered a "universal poll" of its citizens on Saturday to answer this question: "Do you want the Lithuanian state to be an independent, democratic republic?" A similar poll has been called for Estonia on March 3. The Latvian parliament will decide next week whether to hold its own poll.

It was not clear whether Soviet authorities would try to block any separate votes in the republics. Gorbachev's speech came nearly four weeks after the start of a military crackdown in the Baltics that has left at least 19 people dead.

Lithuanian leaders deliberately avoided use of the word referendum. They argue that Lithuania's prewar independence was restored on March 11 last year as the result of a free vote in a democratically elected parliament and does not have to be formally ratified by the population. The purpose of the poll, in their view, is to prevent Moscow from being able to argue that a majority of the population would like to remain within the Soviet Union.

In his television statement tonight, Gorbachev said that separatism and nationalism already had turned millions of Soviet citizens into "second class citizens," creating a refugee problem of huge dimensions.

At a news conference this evening, Russian deputies said that they would try to deprive Gorbachev of using the referendum as a vote of confidence in the central government. Yuri Boldirev, an aide to Russian President Boris Yeltsin, said Russia was considering asking a supplementary question along these lines: "Do you still have confidence in the Supreme Soviet?", the federal parliament.

A tough editorial in the Communist Party daily newspaper Pravda provided further evidence today that the conservatives have gone on the counteroffensive. The editorial called for decisive action to save the Soviet Union from political and economic collapse. "It would be criminal and ruinous if we entrusted the future of this great country to people who are unscrupulously gambling with the fate of whole peoples," it declared, in a clear reference to Yeltsin, who is widely regarded as Gorbachev's rival, and the Baltic leaders.

Some Communist Party hard-liners are now openly demanding the reversal of key reforms such as the legalization of a multi-party system and the attempt to create a market economy. In a page-long interview with the conservative daily Sovyetskaya Rossiya, the party's former ideologist, Yegor Ligachev, denounced Gorbachev for abandoning traditional Marxist concepts such as the class struggle.

Ligachev, who still represents an influential body of opinion within the party even though he was forced into retirement last summer, revealed a series of major political differences with Gorbachev over the past three years. He said that he had written a series of letters to the party's policy-making Central Committee, outlining his disagreements over the handling of ethnic relations, Eastern Europe and the general political situation in the country.

Ligachev said that mistakes committed by the Soviet leadership had contributed to a "major defeat for international socialism" in Eastern Europe. He said that East Germany had simply been swallowed by West Germany, the Warsaw Pact defense alliance had ceased to exist and capitalism was being restored in many East European countries.

The bluntness with which Ligachev laid out his political differences with Gorbachev suggests that he believes that the political struggle is now reaching a climax and he has nothing left to lose.