Negotiators for 4,000 union hotel workers and 14 San Francisco hotels will return to the bargaining table today and Friday at the request of Mayor Gavin Newsom.

Today's bargaining session will be facilitated by a federal mediator, but it won't take place in the context that Newsom had hoped for: On Tuesday, he asked the two parties to agree to a cooling-off period in which employees would return to work while contract negotiations take place, but the effort failed.

With Newsom acting as a conduit Tuesday night, negotiators for the hotels said they would agree to a cooling-off period only if the union removed from the negotiating table its demand for a contract that either expires or can be reopened in 2006. The union, Local 2 of Unite Here, refused. It wants the contract to be synchronized with those of hotel unions around the country to enhance bargaining strength.

"If the union agrees to take that off the table, the hotels would return the workers to their jobs as soon as tomorrow morning,'' said Barbara French, a spokeswoman for the hotels.

"We are willing to agree to a cooling-off period, but we will not allow conditions to be attached,'' said Local 2 President Mike Casey. "That's a nonstarter. I'll tell them, 'You put the workers back to work -- those are our jobs.' ''

A two-week strike against four hotels ended on Wednesday, and a group representing 14 facilities, the San Francisco Multi-Employer Group, kept a promise: At 12:01 a.m. Wednesday, the 1,400 union workers who had struck the hotels were locked out of their jobs. They join 2,600 others who have been locked out of 10 hotels since Oct. 1.

"I'm extremely disappointed that they extended the lockout, and I'm hopeful we can engage in an agreement where both sides have a cooling-off period,'' Newsom said Wednesday.

"The first issue I want to talk about is the lockout,'' union leader Casey said Wednesday, referring to the Thursday session. "In my view, they changed the subject. The struggle is no longer about issues in a contract. This is about our right to have those jobs. It shows how arrogant and callous these guys are and how indefensible their position is.''

Today, in a bargaining session that begins in the late afternoon at Bill Graham Auditorium, it's expected that the hotels will present a revised proposal on health care cost sharing, and wages and benefits. The union will caucus and give the employers a reply but there is no timetable. The response could come in the evening, Friday or later. In addition, the contract duration remains a topic for discussion, the union wanting it to be for two years while the employers are offering a five-year pact.

"The hotels are ready to make a deal,'' said Matt Adams, vice president of the Multi-Employer Group. "The roadblock has been the union's refusal to get off of a two-year deal and off of a national labor strategy that has nothing to do with San Francisco,'' he said.

Also Wednesday, a group of locked-out Fairmont Hotel workers, accompanied by members of the clergy, attempted to enter the hotel in the morning. They met with Mark Huntley, the hotel group's president, while the clergy said a prayer for workers. The hotel refused to let the employees come back to work.

Staff writer Ilene Lelchuk contributed to this report.