The Soviet Union seriously considered a military intervention in Poland last December but key Kremlin leaders were split down the middle on the issue and President Leonid Brezhnev cast the decisive vote against it, according to a report received by American officials.

The officials stressed, however, that the account of Soviet deliberations in early December came from one source and could not be corroborated through other intelligence channels available to the United States.

Some analysts suggested that the account may have been a "purposeful report," that is, another phase in Moscow's campaign of pressure against the Polish communist leadership to put its house in order and deal firmly with the independent trade union federation Solidarity.

These analysts pointed out that similar reports about Politburo divisions on the use of military force circulated before the 1968 invasion of Czechoslovakia.

According to U.S. assessments, there are no indications that the question of military action in Poland has thus far come to a formal vote in the Soviet Politburo. Instead, according to the report received here, it was considered by a group of seven Politburo members who play the principal role in shaping foreign policy and was rejected by the narrowest of margins.

American analysts believe that in addition to Brezhnev, the leaders involved normally in such deliberations include Andrei Kirilenko, who frequently stands in for Brezhnev, chief ideologist Mikhail Suslov, and the Politburo members in charge of the government, security, defense, and foreign affairs.

On matters dealing with Eastern Europe, alternate Politburo member Boris Ponomarev, who is responsible for relations with foreign communist parties, and K.V. Rusakov, secretary of the Central Committee responsible for Eastern Europe, would normally psarticipate in an advisory capacity.

According to the analysts, the account of the December vote in the foreign policy-making group contained "one wrong name."

The score of the account was not disclosed. But it is believed that the information reached the West after the Soviet Communist Party congress in February and that it was based on conversations between West European Communists attending the congress and their Soviet hosts.

Analysts suggested that the reported meeting in early December coincided with electronic and other intelligence reports about Soviet military buildup in the western districts adjacent to the Polish border. As a result, a similar Soviet buildup two weeks ago raised fears here that Moscow may be close to a fateful decision on Poland.

In another development, U.S. officials said they had received reports that Moscow interceded with senior Polish Communist Party officials to ensure that hard-liners in the Polish Politburo would not be purged during a Polish Central Committee meeting two weeks ago.

The offficials said their information does not support accounts from Warsaw quoting Polish sources as saying that a letter from the Soviet Central Committee was read during the crucial Polish session. The letter purportedly urged against any change in the composition of the Polish Politburo and Central Committee.

These officials said it was highly unlikely that such a message would be conveyed in written form and in front of several hundred persons.

In contrast to extreme secrecy surrounding the deliberations within the Soviet leadership, information about Poland's governmental process in more accessible because of the continued turmoil in the country and known divisions within the Polish Communist Party leadership.