Members of a union representing research and technical workers walked picket lines Wednesday at University of California campuses and hospitals in a one-day strike amid a lengthening stretch of unsuccessful contract negotiations.

Some 10,000 members of University Professional and Technical Employees-Communications Workers of America were expected to take part statewide, union spokesman Dan Russell said.

They perform jobs including running clinical trials, assisting in laboratory tests, managing classroom technology and caring for research animals.

"We have gone without any wage increases for virtually two years, for most of us at this point,"said Erin Brightwell, a speech pathologist at UCSF and a member of the union. "So it's quite frustrating, and I think a lot of workers are ready to do something that shows how committed they are to maintain the workforce, the quality of this institution, by having a skilled and stable workforce at the university."

Vermont Sen. Bernie Sanders, who is again seeking the Democratic presidential nomination, was scheduled to lend support with a midday speech at the University of California, Los Angeles, where strikers wearing ponchos marched in rain.

The union and the University of California have been at odds since 2017 over issues including pay, health care premiums and retirement terms.

UC spokeswoman Claire Doan characterized the strike as "organized theatrics."