The late Soviet leader, Nikita Khrushchev, once threatened the West with an atomic attack to retaliate for a Western troop buildup, according to a study by an American historian published recently in West Germany.

Khrushchev made the thinly veiled threat to British Ambassador Sir Frank Roberts in Moscow on July 2, 1961, Said Honore Marc Catudal Jr., a Washington native who teaches at St. John's University in Collegeville, Minn.

Catudal said Khrushchev bluntly told Roberts that "six of his H-bombs would be quite enough to annihilate the British Isles and nine would take care of France."

According to Catudal, Khrushchev's exercise in brinkmanship was the first of several such threats aimed at intimidating the NATO alliance.

The revelation comes in the context of a broader study Catudal did for the Volkswagen Foundation of West German entitled "Kennedy and the Berlin Wall Crisis." Khrushchev's threat came about 40 days before the wall was built.

According to a dispatch filed from Germany by Reuter, the foundation described the study as a "detailed reconstruction of events based on information from hitherto inaccessible sources and secret documents from the White House, CIA and Defense Department."

Catudal, who returned from West Germany Thursday, said he had interviews with former secretary of state Dean Rusk, Gen. Maxwell Taylor and Other high officials, and was granted access to declassified cable traffic because of the Freedom of Information act.

According to the study, President Kennedy and other officials expected the East Berlin government to take strong steps to curb the flow of refugees that was depleting the labor force in the Communist-run country. Catudal contends that statements from U.S. leaders, particularly one comment made by former Senate Foreign Relations Committee chairman J. William Fulbright, actually heped the East Germans justify the building of the Berlin Wall.

Fulbright, asked on a television interview program whether he could accept a closing of the border between the two sectors of Berlin, said: "I don't understand why the East Germans don't close their borders because I think they have a right to close it."

Armed with Fulbright's statement, which they saw as a trial balloon from the Kennedy administration, the East Berlin government persuaded the divided Warsaw Pact nations to approve their decision to build the Wall.

Catudal said the possibility that the Communists might divide Berlin by a wall or barbed-wire fence had been considered by Western intelligence since 1958, but NATO leaders discounted the possibility.

Catudal, 34, who earned his PhD at American University's School of International Service, said Kennedy was ready to risk a war for all of West Berlin, but not to defend the West's right of access to the eastern zone of the city.

Therefore, at a July 13, 1961, National Security Council meeting, Kennedy told then-defense secretary Robert McNamara that the United States would resort to military intervention only if West Berlin itself were threatened, Catudal said.