An international ballet competition will be held here next year--the first major one to be based in New York, the city frequently called "The Dance Capital of the World."

The New York International Ballet Competition Inc. has booked the 2,800-seat City Center Theater from June 11 through July 1, 1984, for what it anticipates will be a once-every-three-years event. Details of the competition are to be announced next Tuesday at a press conference with four well-known ballet dancers: Fernando Bujones and Cynthia Gregory of the American Ballet Theatre and Sean Lavery and Patricia McBride of the New York City Ballet.

The dance gala is the brainchild of highly regarded dance teacher Richard Thomas, who is the father of actor Richard Thomas and actress-dancer Bronwyn Thomas.

The elder Thomas, who has been involved in dance and theater for about 45 years, runs the New York School of Ballet, which he cofounded with his late wife, the famous dancer and coach Barbara Fallis. Bujones, Gregory and Lavery all studied with Thomas or his wife.

"I'm not a great believer in competitions in the arts, but when my daughter went to the Jackson competition, in Mississippi a few years ago ," Thomas said, "she had a great learning experience and a great time with the other boys and girls from around the world."

Thomas said that as a result of his daughter's reaction to the competition environment, and of the success of competitions in other nations, he decided to help stage one in Manhattan.

The competition will accept amateurs and professionals, foreign government-sponsored dancers and privately sponsored performers.

"Everyone is welcome," Thomas said, adding that he hoped dancers from Soviet bloc nations would compete.

Funding for the event is coming from corporate, foundation and private sources, according to Ilona Copen, president of the competition corporation.

It was not clear yesterday how the new competition would fit in with other major international competitions, currently held in Varna, Bulgaria; Tokyo; Moscow; and Jackson, Miss.