The Soviet Union abruptly canceled the American tour of the Moscow State Symphony orchestra today in a move apparently linked to the recent multiple defections of Soviet artists and sports figures to the West.

The cancellation on less than a week's notice was made without explanation. Western sources said it was precipitated by Soviet fears of possible new defections.

The Soviets have been stunned by the defections of five important performers in the past month, and they had sought U.S. assurances that potential defectors would not be granted asylum in the United States as a condition for sending the 170-member orchestra.

An announcement by the Soviet Ministry of Culture said the long-planned tour of 24 U.S. cities was canceled because the orchestra's American booking agent, Columbia Artists' Management of New York, had "failed to fulfill several conditions of agreement."

Columbia Artists was the agent for the Bolshoi Ballet's recent U.S. tour during which three dancers defected. Within a week, two of the world's best known figure skaters, former champions Oleg and Ludmilla Protopopov, both highly decorated Communist Party members, defected to Switzerland.

While the tour of the prestigious Moscow symphony was canceled, Soviet authorities made no move to prevent the U.S. tour of the Moscow State Radio Pops Orchestra. The 70-member orchestra is scheduled to perform in more than 20 U.S. cities next month.

In New York, Samuel Niefeld of Columbia Artists said that the firm was informed by cable that the symphony's tour was off. He said he was "summoned" to Moscow last weekend to discuss the issue, but he refused to disclose details. The orchestra was to have opened its tour next Wednesday at Carnegie Hall in New York.

In Washington, the State Department expressed regret at the cancellation. The Moscow symphony was to have been the first major opening this season at the Kennedy Center, and 3,500 of the approximately 5,000 tickets had already been sold, according to a Kennedy Center spokesman.

A spokesman for the Soviet booking monopoly, Goskoncert, said the tour "is no longer being planned. We don't know [why], it is simply not."

The Moscow symphony was the first Soviet orchestra ever to play in the United States. It made its American debut at Carnegie Hall in 1960 and toured the United States again in 1969, 1970, and 1975.

It has had only one defection, which occurred in 1969, when orchestra member Vsevolod Lezhnev left and eventually joined the St. Louis Symphony.

The recent spurt of defection, however, appears to have generated considerable embarrassment as well as confusion here. Among the Bolshoi defectors were the superstar Alexander Godunov, who bolted the company in New York on Aug. 22. His stand-in Leonid Kozlov did likewise on Sept. 16 in Los Angeles along with his ballerina wife Valentina.

The Protopopovs defected the next day in Switzerland where they were with a Soviet ice show.

Godunov's wife, Ludmilla Vlasova, also a dancer, decided to return to the Soviet Union, however.

Soviet mediat have treated her as a heroine in a spy drama, and said Godunov was enticed to defect by the U.S. intelligence agents with promises of "mountains of gold and rivers of whiskey." Soviet intelligentsia have hooted at the propaganda, saying, as he has himself in recent interviews, that he defected because he yearned for artistic freedom unavailable here, where art is a matter for ideological control by the state. The Soviet media have had no comment on the defections of the other four.

Soviets here have predicted the defections would bring an abrupt tightening of control of Soviet troupes touring the West. Aside from today's cancellation, however, no other similar moves have been reported here. The Bolshoi is scheduled to tour Japan in a few months.

The U.S. Embassy here had already issued visas to the Soviet symphony.

The symphony, one of the Soviet Union's finest, was to have been conducted by Maxim Shostakovich, son of the late composer, Dmitri Shostakovich. One of its guest performers was to have been American Nathaniel Rosen, who won the world-famed Tchaikovsky medal here last year in the cello.

Many famous Soviet musicians now are permanently in the West, such as Mstislav Rostropovich, conductor of the National Symphony and virtuoso cellist, conductor Kirill Kondrashin, and ballet stars Rudolf Nureyev. Natalia Makarova, and Mikhail Baryshnikov.