An FBI attempt to bar a U.S. visit by two Soviet officials, suspected of espionage activities, has held up negotiations on a new U.S.-Soviet cultural exchange agreement and raised fears within the State Department about renewed friction between Washington and Moscow.

At issue is a problem that has brought State and the FBI into frequent conflict during recent months -- the clash between the pursuit of better relations with the Soviet Union and national security considerations.

The two Soviets are members of an official, three-man delegation that had been scheduled to come to Washington this week to begin talks on renewing the agreement under which the two countries exchange visits by prominent musicians, entertainers and other artists.

However, informed sources said yesterday, the FBI opposed giving visas to two of the officials because they were among 105 Soviet diplomatic personnel expelled from Britain in 1971 for alleged espionage activities. The sources were able to identify the two only by the last names of Azarov and Kyrugin.

As a result, the sources said, the State Department was forced to delay acting on the visa requests and to ask the Soviets to postpone the cultural exchange talks until January.

The official reason given by State to Moscow, the source added, was that the International Communications Agency, the main U.S. agency in the negotiations, first wants to conclude similar talks now under way with Romania. However, some sources said, the clash over the two visas was at least as big a cause of the postponement.

Within the State Department, the sources said, the matter has caused serious concern because of fears that rejection of the two Soviets will touch off a cycle of retaliations by Moscow against U.S. officials seeking to visit the Soviet Union on business.

Underscoring that concern, the sources continued, was the recent Soviet refusal to grant a visa to a State Department officer, Martin A. Wenick, who had been scheduled to go to Moscow to assist in advance preparations for the visit there of Treasury Secretary W. Michael Blumenthal beginning this weekend.

Following what the sources called "a high-level U.S. appeal," the Soviets reversed themselves and gave Wenick a visa. The sources said that, while State Department officials are not certain that the two cases are connected, there is suspicion within the department that the Wenick incident was intended to show Moscow's displeasure and impatience over the delay in giving visas to its officials.

In the background is the feeling of many high-ranking State officials that the FBI, backed by an increasingly hard-line approach in Attorney General Griffin B. Bell's Justice Department toward communist-bloc espionage, has been complicating the search for detente with the Soviet Union.

In its most extreme form, this get-tough approach has involved such FBI-Justice actions as the recent arrest and conviction of two Soviet citizens employed by the United Nations on charges of trying to buy U.S. Naval secrets.

The State Department and the CIA, which had argued for expelling rather than prosecuting the two Soviets, contends that Moscow interpreted the incident as a breach of the "unwritten rules" that the two countries normally apply to espionage activities. State officials say that the Soviets' subsequent arrest of an American citizen, Francis J. Crawford, was a direct retaliation for the prosecution of its two nationals.

On a less dramatic, but potentially more important, level, the Justice and State departments also have been at odds over State's alleged permissiveness in granting visas to visitors coming from the Soviet bloc. The State Department argues that its ability to encourage a regular flow of officials, journalists, businessmen and others is an important element in its everyday dealings with Moscow and its allies.

However, the FBI counters that, as part of its responsibility for safeguarding national security, it must keep track of suspect visitors from communist countries. FBI and Justice officials say that they have come under increasingly heavy pressure from Congress to keep potential spies out of the country.

In an effort to resolve the conflict, the Carter administration recently established a special committee composed of representatives from State, Justice, the FBI, the CIA and the Immigration and Naturalization Service to pass on disputed visa requests from the communist bloc.

This committee, headed by Associate Attorney General Michael Egan, is supposed to iron out cases where there is a clash between State and the FBI over whether a visa should be granted. But, the sources said yesterday, there is a danger that the committee will run into a serious impasse over the case of the two prospective Soviet cultural negotiators.

According to the sources, the FBI, citing their 1971 expulsion from Britain, has insisted that the two are a potential security threat and should be denied entry. But those State officials charged with managing U.S.-Soviet relations reportedly are equally insistent that the visas be granted to avoid retaliation.

The sources said the matter is considered so serious at State that Deputy Secretary of State Warren M. Christopher is expected to meet with Bell and Egan within the next few days in an attempt to find a solution.

Since the cultural exchange agreement doesn't expire until next year, there is no urgency about negotiating a new one, the sources said.But, they added, the feeling within the State Department bureaucracy is that the question of the negotiators' visas should be settled quickly in order to avoid a precedent that could greatly complicate a large number of U.S.-Soviet negotiations and exchanges planned for the coming months.