Unifor has set a deadline for its contract talks with General Motors for 11:59 p.m. on Oct. 9.
Negotiations between the union and the U.S. automaker resumed this week after workers at Ford Motor Co. of Canada voted to approve a new contract.
The GM talks cover about 4,300 workers at the automaker's St. Catharines Powertrain Plant, the Oshawa Assembly Complex and the Woodstock Parts Distribution Centre.
Unifor is looking to use its agreement at Ford as a pattern agreement in its talks with GM and Stellantis.
The Ford deal included wage hikes, pension and benefit improvements, and special EV transition measures for workers at Ford's assembly plant in Oakville, Ont.
It also added two new paid holidays.