Mayor Marion Barry moved yesterday to reinforce his intention to hold declaring that wages would not be the subject of collective bargaining this fall.

Unions representing city workers "obviously are not going to be able to bargain for pay" this year, Barry said.

Barry's statement ruling out any formal bargaining for wages before the beginning of the new fiscal year on Oct. 1 came only hours before leaders of the unions held a long -- but ultimately inconclusive -- meeting with the city's Public Employee Relations Board. This is the unit charged with certifying the unions as official bargaining agents to represent various sections of the city work force in negotiations for wages.

Some of the labor leaders emerged bitter and confused from the three-hour meeting at the Martin Luther King Jr. Library. All agreed, however, that they were determined to push for a pay increase in October equal to the 9.1 percent raise proposed for federal workers by President Carter, and not the 5 percent raise Barry has said he is willing to give.

In the past, only teachers, police officers and firefighters have been able to bargain with the city for wages. Pay increases for other city government workers were automatically pegged to increases received by federal government workers. For the last several years, under an agreement worked out by Barry when he was a member of the City Council, police, firefighters and teachers have received identical raises.

Legislation passed in 1978, however, requires that beginning this year, the city must bargain with the unions for wages.

But the Public Employee Relations Board (PERB) is nowhere near finished with its job of certifying official bargaining agents for the workers. fAnd Barry, who originally said he planned no pay increase this year for city employes and only this week said he could grant the 5 percent increase, has said there is no money available to grant the 9.1 increase that federal workers stand to receive.

"It's not a question of whether they deserve, need, are entitled to or want the 9.1," Barry said at a morning news conference. "The fact of the matter is that we don't have in our budget but so much money."

As Barry spoke in his District Building Office, another aspect of the tension developing between the city and the unions that represent its workers was evident on the street five floors below: About 50 Department of General Services workers, represented by the American Federation of Government Employees, picketed the buiding to protest the impending layoffs of 74 workers in the department.

Barry said the only way to guarantee a 9.1 percent increase for city workers would be to lay off even more employes to make additional funds available, or to ask the City Council to vote new tax increases. The mayor said he rejected both approaches.

The labor leaders came out of the afternoon PERB meeting with different notions of what had transpired. And the city's top labor negotiator, Don Weinberg" stance that seemed unlikely to sit well with the unions.

Geraldine Boykin, chairman of the union that represents half the city's work force, said she and other union representatives would meet with Weinberg next Monday to "bargain on the salary issue."

Weinberg said later, however, that the Monday meeting would be "just to talk about the whole issue; it's not a bargaining session." He said no bargaining session with Boykin is possible, since her union, District Council 20 of the American Federation of State, County and Municipal Employees, has not been certified as an official bargaining agent.

Larry Melton, vice president of the police officers' union, said his members are "very bitter" at the prospect of receiving only a 5 percent increase, and other union sources said there already have been grumbled suggestions from members that the union should go on strike.

William N. Hoyle, president of the firefighters' union, said he was" waiting to see what the city will do." William Simons, president of the Washington Teachers Union, said his union is determined to push for the 9.1 percent increase.

Weinberg said the delays in certifyiing unions as official bargaining agents will continue to ensure that employes in different departments who do identical jobs are not paid different salaries. Some workers might fall under the jurisdiction of two or more unions, Weinberg said.

"The issue of pays is always an emotional one," Weinberg said. He said he believed the 5 percent raise offered by Barry makes city workers' salaries "very competitive" with those paid by other local governments in the area.