With hundreds of cafeteria workers, custodians and secretaries poised to strike, the Pittsburgh Public Schools and American Federation of State, County and Municipal Employees head into a key bargaining session tomorrow.

At a meeting at Pittsburgh Carrick High School yesterday, 265 members of AFSCME Local 297 voted unanimously to authorize a strike. Last Tuesday, members of AFSCME Local 2924 voted 163-2 to authorize a walkout.

The labor dispute threatens to disrupt the start of the 2008-09 school year. Eight accelerated-learning academies resumed classes last Monday, and other schools reopen Thursday.

In all, Local 297 represents about 350 custodians, food-service workers, repairmen, truck drivers and other workers, while Local 2924 represents about 200 clerical employees. They have been working under terms of their last contracts, which expired in December 2006.

No strike date has been set, but the votes authorize the union to call a walkout at any time. The union must notify the district 48 hours before a strike.

Richard Caponi, director of AFSCME District Council 84, said he hopes district negotiators will take a message from the strike votes and bring a different attitude to tomorrow's talks. Bargaining also is scheduled for Sept. 2.

"We started bargaining in July of 2006. This is August of 2008. I think that shows a willingness on our part to negotiate a contract without taking some type of job action," Mr. Caponi said.

He said he remains committed to resolving the dispute without a strike and believes a tentative agreement can be hammered out in one meeting. But he added, "The window of opportunity to do a lot of this is closing."

School board member Theresa Colaizzi, chairwoman of the district negotiating committee, said she was disappointed by the strike votes but focused on making progress at tomorrow's talks.

"I'm going to go in there with the attitude that we're going to get this resolved, and I'm hoping the union leadership comes in with the same attitude."

She added that union members "will be hurt the most" by a walkout and said she hopes that the strike votes won't prompt union negotiators to dig in their heels.

Mr. Caponi said the district would have a difficult time operating schools without custodians, food-service workers and other union members; Ms. Colaizzi said the district has a contingency plan.