OAKLAND, Calif. — About 3,000 workers in the Northern California city of Oakland plan to strike starting Tuesday over stalled contract negotiations.

City spokeswoman Karen Boyd said most city programs and buildings will be closed, including libraries and senior centers, for the duration of the strike.

Police are fire services will not be affected.

Members of Service Employees International Union Local 1021 have worked without a contract since June 30. The union says the city is understaffed, underpays and relies too much on temporary help.

Members of an engineers union will also join the strike.

The city says the strike is unlawful. It says the two sides have not reached an impasse and it wants to reach a fiscally prudent, fair contract.

Oakland has a population of more than 400,000.