The American Ballet Theatre's nearly two-month long labor dispute with its dancers ended last night as the dancers voted 57 to 0 to accept ABT's latest offer.

The new contract is estimated by the dancers' attorney to represent an approximate 40 percent wage and fringe benefits increase spread over the next three years.

The dancers are expected to return to work on Jan. 2 and rehearse until the remainder of ABT's cross-country tour begins on Feb. 4. That tour, according to ABT's general manager Joyce Moffatt, will proceed as scheduled. The troupe will perform at the Kennedy Center for three weeks beginning April 1.

The dancers won on most of the key issues in the dispute, and secured for the first time supplementary unemployment benefits, and a job security clause. They also received substantial salary increases, with the lower paid dancers receiving proportionately more than dancers with more seniority. By the end of the contract the lowest paid corps de ballet member will be earning $400 per week as opposed to the current starting salary of $215.

The dancers' attorney, Leonard Leibowitz, called the successful resolution of the dispute a victory for the dancers and a declaration of independence for all dancers in America.

He said "the supplementary unemployment benefits are recognition that dancers have to get paid all year long: The job security clause is recognition of the concept that dancers can't be thrown out without a fair hearing. But the most important thing was that ABT had to sit down with the dancers and negotiate a real contract.

"The settlement shows dancers all over what they can do by getting together.

It shows that the corps de ballet is a star in the aggregate."

ABT's Moffat said that news of the settlement was "absolutely wonderful. I have a great deal of respect for the dancers."

Within the last two weeks, pressure for a settlement had intensified as the Metropolitan Opera Association informed both sides that if there was no settlement by Jan. 1 the Met would begin actively seeking to replace ABT with other performing arts companies. ABT had been booked to perform for a record-breking 10-week run at the Met beginning next May.

Another factor was a secret meeting between ABT's new artistic director, Mikhail Baryshnikov, who will begin his tenure next September, and a group of dancers a few days ago. The dancers' attorney said that the job security issue had been thrashed out at that meeting.

Baryshnikov demanded the right to discharge a dancer for artistic reasons but yielded on several key points. Under the terms of the new contract, dancers may be discharged for "just cause" such as chronic lateness or drunkenness. If Baryshnikov is dissatisfied with a dancer's performance level he is required to give the dancer warning and an opportunity to improve. Even then, he must meet with a committee of dancers before firing anyone.

Under the old contract, weekly salaries for corps de ballet members ranged up to $383 per week after seven years of employment, a spread of $168 from starting salary. At the end of the new contract the range will be from $400 to $475 per week. For soloists, the new salaries will range from $540 to $610.

Minimums for principal dancers, currently $525, will reach $650 per week by the end of then new contract.

The dancers will now have their hotel rooms paid for -- two dancers per room -- when they travel, and receive $20 per day for food.

Beginning with the 1980-81 season, ABT will guarantee the dancers a minimum of 40 weeks per season of work, up from this season's originally scheduled 36 weeks. Supplementry unemployment benefits, paid in addition to unemployment insurance, will begin at $25 per week in the 1980-1981 season, and increase to $50 the following year.

Although the dancers' attorney estimated the new contract to represent a 40 percent increase, a somewhat lower figure is expected to be released by ABT today. The company's management is believed to fear that it will have to match the dancers' increase when its contracts with other unions expire.