Western diplomats here expressed serious concern today about Soviet intentions to set up a national "anti-Zionist committee," saying that the plan could reflect a determination to continue to enforce a recent sharp reduction in Jewish emigration.

A group of prominent Soviet Jews called yesterday for creating such a committee to coordinate an anti-Zionist campaign and combat the influence of Israel and foreign Jewish organizations in the Soviet Union.

A senior diplomat said that the officially sponsored appeal, published prominently in today's editions of the Communist Party newspaper Pravda, may constitute an effort "to build a wall between Soviet Jews and the Jews in the West." He said, "We are very concerned."

The proposal also suggested that the authorities may intend to restrict private Jewish religious and cultural activities that have become widespread since the early 1970s. At that time, the Russians agreed to allow large numbers of Soviet Jews to emigrate in exchange for promised U.S. trade concessions.

Jewish cultural and religious activism apparently now is regarded as one of the important elements in sustaining the emigration drive. The establishment of an "anti-Zionist committee" is seen by observers as foreshadowing a government-backed drive to persuade Jews waiting for exit visas to withdraw their applications and at the same time dissuade others from applying.

In Washington, the State Department issued a sharply worded statement condemning the Soviet appeal as anti-Jewish and anti-Israeli propaganda. "The basic thrust of this and other 'anti-Zionist' propaganda is anti-Semitic," it said.

There are indications here that the authorities have decided virtually to cut all Jewish emigration despite efforts by American and Israeli organizations to put pressure on Moscow to ease its policies.

From its peak in 1979, when about 50,000 Soviet Jews were allowed to leave, the rate of emigration has slowed to a trickle. In 1982, according to figures provided by the British National Council on Soviet Jewry, only 2,692 Jews left the Soviet Union for Israel.

During the past six months, the number of departures has continued to drop and has been far lower even than the 1982 average of 224 exits a month. According to figures supplied by Jewish organizations, only 81 Jews were allowed to leave the Soviet Union in January.

In previous years, the authorities sought to cut the flow of emigrants by introducing a number of bureaucratic practices that reduced the chances of gaining permission to emigrate. At some time last summer, the authorities apparently decided that such bureaucratic steps were not sufficient to deter potential applicants.

The eight prominent Soviet Jews who signed the appeal, including decorated hero Col. Gen. David Dragunsky, said that an "anti-Zionist" national committee should be established to conduct "a decisive struggle" against western and Israeli Zionists who purport to campaign on behalf of Soviet Jewish citizens.

Their statement said that Soviet Jews were a fully integrated part of Soviet society and that only foreign Zionists were making "slanderous" claims that Jews suffered problems here. Addressed to the entire Soviet people, the appeal called on all organizations and individuals to take part in mounting a "decisive resistance" to the "machinations" of "Zionist forces."

Preceding yesterday's appeal was a series of articles in recent days focusing on Jewish emigres who had returned to the Soviet Union or those who had obtained exit visas but nevertheless had decided to remain here.