The Soviet Union will enter a horse in the Washington, D.C. International for the first time in 21 years in a move Laurel Race Course's president, Frank J. De Francis, said will help reestablish the event as a major turf classic.

He said yesterday he received a cable this week from Soviet racing officials who accepted his invitation to enter the race and confirmed they will send that country's top two thoroughbred horses to Laurel to train three weeks prior to the 36th running of the International on Oct. 31.

De Francis said the Soviets will select one of their two horses -- and their own jockey -- to run in the race after the training period. Laurel will pay the Soviet airline expenses. Two other horses will be invited by Laurel officials, one likely from South America and one from either Australia or New Zealand.

The rest of the field will come from U.S. horses which have been nominated for a fee of $10,800. The nominated horses will race for a purse of $750,000, with $450,000 going to the winner. The three invited entries, under a two-tier purse structure, will race for a purse of $400,000, with no entry fee, and a winner's share of $240,000.

"I consider the Soviet acceptance an absolute coup in our effort to rebuild the foundation of this race," De Francis said, adding he also was positioning the $250,000 Selima Stakes for 2-year-old fillies and the $250,000 Laurel Futurity for 2-year-old colts the day after the International in hopes of making the weekend even more attractive for fans.

He said among the horses who have been nominated for the International are Manila, Triptych, Dance of Life, Theatrical and the Maryland-bred Broad Brush.

He said the increase in purse money (up from $250,000 in 1985) gives him leverage to seek corporate sponsorship of the event. He also expects the race to be televised this year by one of the three networks.

The Soviets ran at the International from 1958 through 1964 and then again in 1966. They haven't raced here since.

While bloodlines and the level of thoroughbred horse racing competition in the Soviet Union and other Communist countries are considered inferior to Western countries, Soviet horses have fared surprisingly well inthe International. Zabeg ran third in 1960, only three lengths behind American champion Bald Eagle. Aniline third in 1964, came back two years later and led all the way before finishing second behind Kelso. Last year, Laurel invited the Polish horse Korab, reportedly the best from the Eastern Bloc. He was a soundly beaten eighth.

In recent months, the Soviets have sent a basketball team to the United State to work with the Atlanta Hawks and have indicated they may be willing to allow their hockey and basketball players to play here professionally after the 1988 Olympics.