ANN ARBOR, Mich. (AP) — The University of Michigan said striking graduate student instructors would likely lose their jobs if they don’t return to work for the fall term.

It is the latest salvo in a labor dispute that’s been ongoing since a strike by the Graduate Employees’ Organization began in March, near the end of spring term. The union negotiates on behalf of more than 2,000 members, though not all walked off the job.

Fall classes begin Aug. 28.

Graduate students still striking will “likely be removed from the system as a course instructor,” Provost Laurie McCauley said in an email Monday.

“When instructors choose not to fulfill their teaching responsibilities, it disrupts students’ education, damages the quality of instruction, and can cause other harm,” McCauley said. “This is a serious breach of the trust that our students place in us as educators and in their reliance on the institution to deliver on our educational mission.”

Union spokesman Amir Fleishmann called it an “underhanded” tactic.

“We feel confident that it is not going to work,” he told The Detroit News. “Our members are not going to be scared by these threats the university continues to make.”

The university said it recently offered annual raises of 8%, 6% and 6% over three years, plus a $1,000 bonus. The school said the union didn’t respond by last Friday.