OAKLAND, Calif. — A union representing nearly 15,000 researchers, technical employees and health care professionals for the University of California has reached a tentative deal on their contract with the system.

The University Professional & Technical Employees union approved the proposed contract Friday night, calling the deal historic. Workers at UC's 10 campuses and the Lawrence Berkeley National Laboratory will vote on it this week. Union workers include clinical lab scientists, social workers, pharmacists, staff research associates, computer resource specialists, editors and writers.

The proposed four-year contract includes cost-of-living increases of 11.5 to 13 percent, in addition to regular step increases.

Workers would contribute an additional 1 percent to the pension plan to maintain it as is. Union president Jelger Kalmijn said the pension agreement was especially a "breakthrough" because it prevents a two-tiered pension system that would have pushed back retirement with similar benefits for workers by five years.

UC spokeswoman Shelly Meron called the agreement fair and the result of two years of hard work.

"It's been a long road and we're really pleased we've been able to work through these issues and negotiate a fair agreement with our employees," Meron said.

Meron said the system also reached agreements with unions representing nurses, lecturers, librarians and police officers in the last two months.