LOS ANGELES (AP) _ The union representing striking janitors reached a tentative contract agreement Saturday night with 18 cleaning companies, negotiators for both sides said.

However, the 8,500 janitors will continue their nearly three-week-old walkout until they vote on the proposed deal Monday, union President Mike Garcia said.

Officials for both sides refused to release details pending the ratification vote but said they were pleased with the proposal.

``It's a good deal, but we can't comment more than that,'' said Garcia, president of Service Employees International Union, Local 1877.

The ratification vote will come three weeks to the day that janitors walked off the job throughout Los Angeles County.

``I think it's a decent deal for both sides,'' said Dick Davis, chief negotiator for nine of the 18 cleaning companies. Those firms represent 97 percent of the affected buildings.