The current contract with the Canadian Auto Workers, which covers some 17,550 GM workers, expires Sept. 20, the Detroit News reported Wednesday.
GM says its Canadian labor costs have been climbing 5.7 percent each year, and the unprofitable automaker says it can't afford similar raises now.
"I'm not looking to roll back labor costs per se, but I'm certainly looking to control it at zero increase," said Al Green, GM's top negotiator, as talks began Tuesday.
He said the big carmaker isn't seeking rollbacks in wages or benefits, adding "we are not looking for a concessionary agreement."
But he said GM, which has seen its Canadian profits fall to about $500 million last year from some $2 billion four years ago, must find savings to mitigate that decline.
Canadian labor rates are the second-highest of the 18 markets where the automaker builds cars and trucks, the carmaker says.
The union says the base wage for GM's workers in Canada is $24.44 an hour.