Nearly 13,000 technical workers have announced plans to strike the five University of California medical centers, including UC San Francisco, on May 21 and 22.

But UC officials said they will seek a restraining order to block the strike, arguing that it poses a threat to public health and safety and that the union has not exhausted all other options.

Members of the American Federation of State, County and Municipal Employees Local 3299 said they are taking the action to protest nearly a year of stalled contract negotiations.

The union has created a patient-protection task force to help ensure that patient needs are met during the walkout, its leaders said.

In 2008, after the union announced a similar strike against UC medical centers, the Superior Court of San Francisco issued a restraining order prohibiting it.

The current dispute involves pay, benefits, working conditions, limits on contracting out jobs and pension reforms.

The union represents respiratory therapists, nursing aides, MRI technologists, licensed vocational nurses, surgical technicians, diagnostic sonographers, pathology lab technicians, hospital assistants, pharmacy technicians and other workers.