Soviet President Leonid Brezhnev endorsed the results of the Polish Communist Party Congress tonight and expressed the belief that the Polish party is "undoubtedly capable" of mobilizing forces against "anarchy and counterrevolution" threatening Poland.

Brezhnev said the congress, which ended in Warsaw yesterday after votes that replaced the majority of its leadership and reaffirmed reforms adopted in the past year, has "set the task of stabilizing" the situation in Poland and taking the country out of crisis.

The Polish party, "as the leading force of Polish society, firmly following the principles of Marxism-Leninism, is undoubtedly capable of rallying all working people and mobilizing them for a resolute rebuff to anarchy and counterrevolution," Brezhnev said.

In a telegram also signed by Premier Nikolay Tikhonov and distributed by the news agency Tass, the endorsement of the congress program was coupled with the warning that Poland was in "a complex political situation" and that domestic and foreign antisocialist forces are continuing "their subtle attacks on the foundations of the Polish state" as well as "provoking complications in Poland's relations with its true friends."

The telegram was addressed to "the Polish leaders," and it came after the Soviet press blossomed earlier today with reports about the congress that put a generally positive face on what the Kremlin sees as the still unclear course of future developments in Poland.

The Soviet leader's message on the anniversary of the Polish Republic appeared designed to encourage the new leadership in Warsaw to live up to what is seen here as a fresh opportunity for the Polish party to restore its authority in the country.

The tone of press dispatches and broadcasts, coming after almost 10 days of virtual silence about the Polish congress, appeared to reflect the basic compromise struck between Moscow and Warsaw.

The Polish leaders were quoted at length pledging allegiance to the Warsaw Pact and the Soviet Union. Soviet comments in turn said the congress has preserved the "ideals" of Marxism-Leninism while taking into account "the existing conditions" in Poland.

Nevertheless, doubts were expressed as to whether the Poles will be able to translate words into deeds. Viktor Grishin, the Soviet delegate to the congress, said before leaving Warsaw today that the Polish party has faced some "important" issues and "life and practice will show to what extent it proved possible to resolve them."

There are hints here that the Kremlin sees some form of political pluralism in Poland as inevitable, although only at the government level, not in the party. The Russians seem to have reconciled themselves to this as the price of getting Poland's economy moving again.

"If the French can take Communists into the Cabinet," said one senior Soviet Political commentator privately, "perhaps the Poles can take some Socialists into their government."

The Kremlin's attitude toward the question of the leading role of the party is still ambiguous. But the Soviets apparently hope that a government incorporating various Polish factions would satisfy pressures for political pluralism and leave the party outside the realm of basic reforms.

All this does not appear to signify any new Soviet tolerance but rather a realistic assessment of Polish developments and the overriding objective from Moscow's point of view to restore social and labor peace in Poland.

The main fear here is that continued deterioration of the Polish economy -- if it is not reversed soon -- could eventually lead to a total economic breakdown, producing disorders and possibly anticommunist riots. In such a case, the Soviets may be forced into a situation in which they would have to intervene and take the consequences, which are generally perceived as catastrophic.