The American Ballet Theatre yesterday canceled its Kennedy Center season in the face of its inability to reach agreement on a new contract with its dancers. The company had locked the dancers out on Oct. 29.

Reliable sources said, however, that the final two weeks of the season could still be salvaged if a labor agreement is reached within the next few days.

The season was to run for four weeks beginning Dec. 4.

Joyce Moffatt, ABT's general manager, announced in New York, "We have canceled Kennedy Center and we will not open on Dec. 4. We have reached a true impasse" with the dancers.

Martin Feinstein, the Kennedy Center's director of opera and ballet, estimated the loss to the Kennedy Center at about $15,000 in advertising and subscription costs, $29,000 for each week the Opera House is unused, and an as-yet-undetermined sum for notifying ticket purchasers and making refunds.

With little more than two weeks to find a substitute for the ABT and with no certainty that the entire four-week run, as opposed to the opening, would be canceled, Kennedy Center officials were left in a state of uncertainty last night after the announcement.

"The wording does leave open the possibility that they may be able to come in with the 'Nutcracker' around Dec. 18," said a Kennedy Center spokesman, referring to the Tchaikovsky ballet which is a perennially strong Christmas attraction.

"Otherwise, in the limited time available, it seems almost impossible to book a new attraction, get out the ads and sell tickets."

Martin Feinstein, who has booked some of the world's leading opera and dance companies into the Kennedy Center, indicated that he has not yet chosen any substitute for the ABT booking.

"Naturally," he said, "we're very disappointed. We will simply have to see what can be done."

"Despite his repeated denials as late as yesterday afternoon that he had held no discussions regarding the availability of other attractions to fill in for ABT, it had been widely rumored that Feinstein had done so.

Yesterday afternoon, Mel Howard, the promoter sponsoring the U.S. tour by the International Ballet of Caracas, Venezuela, a company which is now performing in New York, confirmed that he had discussed the possibility of bringing the Caracas troupe to the Kennedy Center.

Howard said that in a conversation with Feinstein last Friday he was told that the Caracas company, if it were to perform at the Kennedy Center, would have to use a live orchestra. In New York, with the exception of a few solo instruments, the troupe has been dancing to recorded music.

Howard said he would accept a firm offer from the Kennedy Center, would engage Bolshoi Ballet defectors Elonid and Valentina Kozlov as guest stars for selected Washington performances, and that he would be prepared to fly the Caracas company's conductor and orchestrations to Washington from Venezuela.

Another rumor, that the Kennedy Center is considering substituting a musical for ABT, could not be confirmed last night.

Officials of ABT, its dancers' negotiating committee and the Kennedy Center all agree the outlook for a new quick settlement is "grim." No new negotiating sessions are scheduled.

The dancers are planning an emergency fund-raising benefit for Dec. 23 in New York and reported that since the lockout began, they have received over $22,000 in contributions to the dancers' aid funds. They had previously contributed some $18,000 of their own money to the fund.

ABT's current position is that its latest proposal be submitted to the entire dancers' bargaining unit for a vote -- that proposal calls for arbitration of the dispute. The dancers' negotiating committee over the weekend polled all the dancers and said there was unanimity in rejecting arbitration.

The dancers' attorney, Leonard Leibowitz, said that the difference between the latest offers made by both sides amounts to approximately $300,000 to $400,000 spread over a three-year period -- slightly more than $100,000 per year.

Anthony Bliss, executive director of the Metropolitan Opera Association, who earlier this year said that the Met had saved ABT from folding by giving the company extended playing time at the Met beginning in 1977 -- a contention generally accepted in the ballet industry -- expressed concern about ABT's spring New York season.

"Within a very few weeks we would have to start advertising and promoting the spring season -- before Christmas. I would be troubled if the settlement does not come within the next two to three weeks. There is a great deal of unfortunate bitterness" between the company and the dancers, Bliss explained, cautioning that "we will have nothing to do with this [labor dispute] unless both sides ask us."

ABT is scheduled to perform for 10 weeks at the Met beginning May 5 -- prime performing time, which ABT's board chairman has confirmed has generated a profit for the company in previous seasons.

Last night ABT's Moffatt said, "The future is uncertain."