DETROIT—A strike that could have halted production of some of General Motors’ most profitable and important vehicles has been narrowly averted.

About 15 minutes before a 10 a.m. strike deadline June 30, GM and the UAW reached a tentative agreement for a new contract for about 600 of GM’s Subsystems Manufacturing LLC employees.

The details of that agreement are not yet known.

“The UAW will now focus on the ratification process,”   GM spokesman Dan Flores said in a statement. “We won’t be discussing details of the tentative agreement until the ratification process is complete.”

The subsystem employees have a different contract than that of the 48,000 GM hourly workforce in the U.S. that went on strike in 2019.

The subsystem workforce’s contract expired 14 months ago and after repeatedly failing to reach an agreement on a new contract, the UAW set a strike deadline of June 30 for the subsystem workers at the company’s Flint Assembly, Factory Zero, Lansing Grand River and Orion Assembly plants.

“This negotiation was drawn out and hard fought,” said UAW Vice President Terry Dittes, who is director of the union’s General Motors Department, in a statement. “We look forward to presenting the tentative agreement to members for their ratification.”

The subsystem workers’ strike could have brought production of GM’s most profitable vehicles to a standstill within hours. Subsystem workers sort all the parts that come into the plants and then deliver those parts to the assembly line to keep production humming.