Canadian labour union Unifor said early on Tuesday it would begin strikes at three General Motors facilities in the country after it failed to reach a deal on a new contract to improve wages and pensions by a midnight deadline.

Unifor, which represents about 4,300 workers at GM covered by the contract talks, said it would go on strike at the Oshawa assembly complex, St. Catharines powertrain plant and the Woodstock parts distribution centre.

"This strike is the result of the company’s unwillingness to agree to the union’s core pattern demands on pensions, as well as supports for our retirees and making sure full-time temporary part-time workers are given a clear path to permanent employment, among a series of other unresolved issues," Unifor leaders said in a joint statement.

GM did not respond immediately to a request for comment.

Unifor represents about 18,000 workers at the Canadian facilities of the Detroit Three automakers, which also include Ford and Chrysler parent Stellantis.

The union last month ratified a new three-year contract with Ford that offered wage increases of up to 25% to more than 5,600 workers at its Canadian facilities. Unifor had threatened to strike at Ford was able to reach a tentative deal without doing so.

Unifor said last week that GM was "resisting" a number of important elements of its agreement with Ford.

The union had chosen the company as its second bargaining target of the Detroit Three automakers after Ford.

(Reporting by Shivansh Tiwary and Jyoti Narayan in Bengaluru; Editing by Christian Schmollinger and Jamie Freed)