Unifor, which represents more than 20,000 autoworkers, is pushing General Motors Co (>> General Motors Company), Fiat Chrysler Automobiles (>> Fiat Chrysler Automobiles NV) and Ford Motor Co (>> Ford Motor Company) to invest further in the province of Ontario, home to nearly all of Canada's auto industry, in talks that began this month.

Members voted close to 100 percent in favor of granting Unifor a mandate to strike, according to a statement from the union.

That means workers are in a position to walk off the job if the parties cannot come to terms. The union's current four-year contract with automakers expires on Sept. 19.

Unifor President Jerry Dias has said the union is asking for higher wages and would not agree to a deal unless GM commits to building new vehicles in Oshawa, and Ford decides to keep its engine plant operating in Windsor.

GM's Oshawa plant could shut one of its two assembly lines, with several vehicles already produced elsewhere or expected to move in 2017.

Between 2001 and 2013, some 14,300 jobs were lost in vehicle manufacturing in Canada, according to Hamilton's Automotive Policy Research Center. Some automakers have found cheaper labor in places such as the southern United States and Mexico.

GM Canada has said the negotiations are separate from the carmaker's future investments because labor is not the only cost it considers when deciding where to make new products.

GM said it will make future product decisions for Oshawa only after a labor agreement.

Automakers, however, had agreed to make investments during bargaining with the United Auto Workers in the United States. GM's 2015 deal with the UAW generated $1.9 billion in additional investment in U.S. plants.

GM, Fiat Chrysler and Ford did not immediately respond to requests for comment.

(Reporting by Ethan Lou in Toronto; Editing by Bill Trott)