IF AN October tryout on Broadway is artistically, critically and financially successful, a major ballet company may be created that will tour America and the Western world.

Plans for the new company have been drawn in secrecy over the last several months by the Nederlander Organization. The Nederlanders are the nation's largest private, for-profit ballet impresearios, the operators of nearly 30 live-attraction theaters, and frequent investors in and producers of Broadway shows.

When asked late last month whether he had decided to start a new ballet company, the organization's head, James M. Nederlander, would say only, "Not yet. Nothing definite has been arrived at. It's just in a nebulous stage."

But a four-week engagement at Broadway's Uris Theater in October is now certain. And although some key contracts are not yet signed, a 32-member company is being built around ballerina and choreographer Natalia Makarova -- the defector from Leningrad's Kirov Ballet who is currently a member of American Ballet Theatre -- and a group of various superstar dancers reportedly including ABT's Fernado Bujones and Anthony Dowell, an unnamed star dancer from the New York City Ballet and several stars from Europe.

Makarova has a substantial say in the artistic aspects of the venture, which for the the October run will offer two separate programs -- including at least two sumptuous new productions -- with each program running for two weeks.

Makarova has refused comment on the subject of the company, although officials at the Nederlander Ogranization have confirmed that she will appear on Broadway for four weeks and dance at every performance in the Nederlander-sponsored engagement. Bujones has confirmed that he will appear for two weeks of that run. Dowell's manager referred queries to the Nederlander Organization, which declined to provide any specifics on the October performances.

Informed observers say that the engagement is being viewed as an experiment by the Nederlanders -- and that if it succeeds, the Nederlanders and Makarova will commit to building a permanent institution.

For the October run, some 20 corps de ballet members have already been picked by audition from among those dancers who will be available at the time.And all of the star dancers involved in the presentation will either be performing during layoff time from their home companies or have secured leaves of absence from those troupes.

One ABT board member, who has learned of the new venture, expressed concern that it ultimately could provide substantial competition to ABT. In theory, such a new company would also be competing with the New York City Ballet, and it is believed that one reason for the secrecy surrounding the new company is that the Nederlander-Makarova troupe -- which is still unnamed -- will initially be borrowing dancers from these other companies.

Makarova is said to be interested in starting a ballet school to rectify what she believes is the inadequate training of many American dancers. The school would be in the tradition of the Kirov ballet-affiliated academy, and could feed dancers to the new company.

Despite the deficits regularly run up by Americahs major ballet companies, Nederlander officials reportedly believe that a properly managed troupe, liberally sprinkled with superstar names and an exciting repertoire can turn a profit.

Asked about the potential of dance in America, James Nederlander said in an interview last month that "Ballet is something that is growing and will continue to grow, and many other forms of art may not. There is money in culture if you give people quality. Dance is entertainment. That's what it really is, and I expect that dance in America will get bigger."

And of course booking -- which customarily presents sinficant difficulties for all companies that wish to tour, and therefore must find local theaters -- is no handicap for Nederlander. As he said, "I got into presenting dance because I have a lot of theaters and I have to fill them. Some people like oranges and some like apples -- but you have an audience for everything that's well done."

This is not the first time that the Nederlanders have sought a resident dance company. Several years ago James Nederlander offered the Joffrey Ballet a permanent base at the Uris. At the time, Nederlander wanted to use the Uris soley as a dance theater but the Joffrey refused his offer.

And the Nederlanders already own a number of ballet productions -- costumes and scenery -- which they had built for the Broadway presentations of Rudolf Nureyev and the various ballet and modern dance companies that performed with him.