Superstar ballerina Natalia Makarova and ballet impressario James M. Nederlander yesterday jointly announced the formation of a major new ballet company, to be headed by Makarova and sponsored in the United States by Nederlander.

The troupe in a four-week run beginning Oct. 7 and is expected to tour America and the Western world in future seasons.

According to the Nederlander Organization, six superstars plus Makarova will be featured during the Broadway engagement -- including Anthony Dowell, Peter Schaufuss and Fernando Bujones.

In a prepared statement, Makarova and Nederlander said that the ballerina "conceives this company as a place where talented young dancers under her guidance will have the opportunity to grow through direct stage experience in performances with already established dancers of distinction." The company's 20-member corps de ballet consists of young American dancers.

According to the announcement, the initial repertoire for the new troupe will be "almost entirely composed of productions not previously seen" in America, including two world premieres, two U.S. premieres and two new stagings of rarely performed classical ballets. No additional details on the repertoire were released.

"An American tour as well as engagements abroad are being considered" for the 1981-1982 season, the announcement said.

Makarova could not be reached for comment yesterday, but the ballerina recently said she is not severing her ties with the American Ballet Theatre and will perform with ABT for part of next season.

There have been persistent industry rumors that Makarova had been encouraged in the new venture by Lucia Chase, co-founder and co-artistic director of ABT, who was pressured into relinquishing her ABT position unsuccessfully campaigned for Makarova to succeed her.

Reached last night by telephone, Chase confirmed that she had known of the new company, and said of Makarova, "I'm very much involved with her in everything she does," but will not participate in the new ballet company.