Contract negotiations between the American Ballet Theatre and its dancers broke down last night, and ABT stated it will lock the dancers out Monday morning if a new contract is not signed by then. The old contract expired on Aug. 31.

The lock-out, ABT's attorney Alan Faffe said was planned to avoid a dancers' strike just before ABT's Kennedy Center season, a four-week run scheduled to begin Dec. 4.

"Had we been struck on the opening night of the Kennedy Center season, which we have every reason to believe would have happened, ABT would lose hundreds of thousands of dollars," Jaffe said.

Martin Feinstein, who arranged the ABT appearance for the Kennedy Center said eariler yesterday that ABT was keeping him informed on the negotiations, and that "It's very unlikely we could get [another attraction] this quickely. I have a feeling we would be stuck" if there is a lock-out of a significant duration.

He stated that the Kennedy Center -- which is taking no role in negotiations -- stands to lose its investment "in very expensive advertising," in the cost of making ticket refunds and in the overhead of an empty opera house if ABT is unable to fulfill its Washington engagement.

Joyce Moffatt, ABT's general manager, was uncertain about the Kennedy Center engagement: We haven't thought that far ahead."

No new negotiations are scheduled, and at yesterday's sessions, according to ABT's Jaffe, the dancers "increased their proposal" to approximately a 50 percent wage increase from their previous demand of 40 percent. The new proposal, he said, adds up to a 75 percent total increase in wages, fringe benefits and other costs over two years. ABT has offered a 22 percent package over a three-year period, including a 20 percent salary increase.

Currrent starting salaries for ABT dancers range from $235 per week for a first-year corps de ballet members to $523 for a principal dancer. The company's stars and guest stars, however, are paid by the performance, with some fees reportedly in excess of $3,000 per performance.

Several ABT dancers active in the negotiations -- who asked that their names not to used -- complained about the fees received by the company's Russian defectors.

Two of the dancers claim that Bolshoi Ballet defector Alexander Godunov -- scheduled to make his post-defection debut on Dec. 7 at the Kennedy Center -- is rumored to be getting over $130,000 for the upcoming ABT season, receiving large payments at the expense of the lower-paid American performers. The dancers' negotiating committee raised this issue during the contract talks.

ABT's Jaffe said it was "very unlikely" that a contract would be signed before the Monday lock-out deadline -- which is the start of rehearsals for Abt's 1979-1980 season -- although "we are willing to meet any time, any place, anywhere" with the dancers.

One dancer said, "the musicians get the money, the Russians get the money -- well, it's time for us. We don't care what happens, we can't live on what they're offering. We have to eat too."

If ABT shuts down, it would be the first lock-out or strike in the company's 39-year history, ABT's Moffatt said.