Fifty-six of the 91 cleaning workers fired last month in a cost-cutting move at American University will be hired with full pay and most fringe benefits March 7 by a private contractor who now handles the janitorial chores, university and union officials announced yesterday.

The workers' jobs were abolished Jan. 7 when the university hired the private contractor, Unified Services Inc., a local minority-owned business, to take over its cleaning services.

The agreement, announced at a campus news conference yesterday, provides the workers jobs with Unified and commits the university to paying a wage differential for a year so the workers suffer no loss in pay. Unified pays $4 hourly, while some university cleaning workers earned up to $6.

The agreement followed weeks of negotiations between university officials and Local 25 of the Hotel & Restaurant Employees Union, which had filed unfair labor practice charges against American with the National Labor Relations Board, alleging that the workers were fired for trying to unionize.

The NLRB charges will be dropped as part of the settlement announced yesterday, said union president Minor W. Christian.

About 20 of the 56 have already been hired by Unified, said Donald G. Triezenberg, the university vice president for development and planning.

Unified's president, Jerry Davis Jr., who signed the agreement, could not be reached for comment.

Triezenberg said the university probably would realize no savings in the first year of its $800,000 contract with Unified because the university must pay the wage differential, unemployment benefits and other costs. But he said American would save at least $250,000 yearly afterward.

However, Christian said the union plans to organize the workers, seek higher wages and expand the work force. "I don't see how they can cut from 91 to 56 unless they plan to leave some dorms dirty," Christian said.

Of the original 91 workers, more than 20 have already found new jobs off campus, officials said. After the 56 are hired, on the basis of seniority, the remaining workers will be placed on a waiting list for jobs with Unified.

The agreement retains health and life insurance, pension benefits, and a tuition program under which the employes and their family members can pursue degrees at American without cost.