SAN FRANCISCO (AP) — Thousands of University of California nurses, pharmacists and other medical staff joined walkouts by service workers again Wednesday, forcing medical centers to close and reschedule thousands of appointments and surgeries.

The three-day strike was called last week by American Federation of State, County and Municipal Employees Local 3299 when the union and the university couldn’t agree on a new contract.

READ MORE: Woman Dies in Saturday-Morning Rollover Crash on I-580 in Oakland

The union represents 25,000 cooks, truck drivers, gardeners and other service workers.

Another 29,000 medical staff joined the sympathy strike Tuesday and Wednesday.

READ MORE: Suspect Killed In Unincorporated Hayward Deputy-Involved Shooting

University officials say service workers are already paid at or above market rates and cannot justify the nearly 20 percent raise over three years the union demands.

The UC system includes five medical centers and three national laboratories and has 190,000 faculty and staff and 238,000 students.

MORE NEWS: Big Rig Driver, CHP Officer Rescue Worker Trapped By Burning Truck

© Copyright 2018 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.