A tentative agreement, reached last Saturday between GM and Unifor on behalf of 4,600 union members in Canada's most populous province, Ontario, is pending members' approval.
Both Unifor and GM's Canadian division declined comment ahead of members' vote to ratify the agreement on Saturday and Sunday.
The United States has held talks with its northern neighbor to reduce U.S. tariffs on Canadian-produced vehicles from the current 25%, but talks ended last week over unresolved issues, such as whether to cut duties on medium- and heavy-duty vehicles.
Canada has said it cannot accept a trade deal with the U.S. unless the agreement ensures the survival of a robust Canadian auto assembly and parts industry.
U.S. President Donald Trump has said he will increase tariffs on all Canadian cars and trucks, automotive parts and steel to 50% starting January 1, 2027.
GM would assemble a heavy-duty pickup at an Ontario plant as part of a tentative deal with a key union, marking a boost for Canada's auto sector that has been under pressure from U.S. tariffs.
GM plans to spend C$144 million ($104 million) to add the next-generation heavy-duty GMC Sierra truck to a plant in Oshawa, Ontario, and pledged not to immediately sell or close a second assembly plant in Ingersoll, Ontario, according to a bargaining report on Saturday from the union, Unifor.
