More than 200 employes of the AFL-CIO returned to work yesterday under an arrangement in which federal mediators began efforts to settle a strike by 12 AFL-CIO workers whose Jan. 1 walkout had virtually emptied the headquarters of the labor federation.

Members of The Newspaper Guild and the Office and Professional Employees International Union, two unions that represent AFL-CIO office workers, decided to return to work after the 12 strikers temporarily withdrew their picket line and the Federal Mediation and Conciliation Service began negotiations to end the strike.

The strikers, employed by the AFL -- CIO's food and allied service trades (FAST) department, withdrew their picket from one of two entrances to the building at 815 16th St. NW, allowing hundreds of office workers to return, according to AFL-CIO spokesman Murray Seeger.

Headquarters employes had refused to cross strikers' picket lines, but the 12-member unit, which belongs to The Newspaper Guild, released the other employes from their pledge to honor the picket line, Seeger said.

The FAST employes are researchers, health specialists, analysts and clerical workers who earn an average of $16,000 a year and struck for higher pay, asserting that they should be paid substantially higher salaries to match other AFL-CIO staffers.

The AFL-CIO filed a petition with the National Labor Relations Board asserting that because FAST is a separate employer from the labor federation, the strikers could not legally picket a side entrance on I Street that the AFL-CIO had designated for nonstrikers. The NLRB has not yet acted on that petition, but the picketers late yesterday confined their line to the main entrance.

"This strike is about pay equity, and it is hypocritical that the AFL-CIO is always backing equal pay for workers and here it is trying to wash its hands" by setting up a separate entrance and trying to stop the picketing, said a FAST striker who asked not to be identified. Spokesmen for the strikers were not available for comment.

Several top AFL-CIO officials said privately they blamed FAST President Robert Harbrant for allowing the strike to occur without first seeking mediation. Harbrant said he was optimistic the strike would be resolved quickly and declined to comment on the issues.