The head of the union representing workers at a General Motors plant slated for closure said Premier Doug Ford offered assurances Monday that he would pressure the automaker to change its plans for the facility in Oshawa, Ont.

Unifor President Jerry Dias and Ford had initially clashed over the fate of the facility east of Toronto, with the premier saying little could be done to alter the minds of GM executives. But after a meeting at the Detroit auto show, Dias said the premier had vowed to press the company this week to keep the plant open.

"I was quite pleased when he said he would roll up his sleeves in his meetings he was to have with General Motors and he would be very aggressive in having them change their position," Dias said. "This is a good step forward as we build allies with both levels of government."

The planned closure of the plant at the end of this year would leave 2,600 workers without a job.

Dias, who has been pushing for a reversal of the company's plans, said he was able to explain to Ford that the union's collective bargaining agreement had a clause prohibiting closures during the life of the deal.

"I'm pleased the premier has taken the position that this is not a fait accompli because it's not," Dias said. "People make bad decisions every day and then they change their mind."

Ford said in a statement after the meeting that he had a "constructive dialogue" with Dias in which they had discussed how they could work together.

"Workers are the backbone of our economy and Ontario has the very best in the world," he said. "Creating good-paying jobs for the hardworking people of Ontario will continue to be my top priority as I engage with the auto industry in Detroit this week."

Ford will sit down with GM executives Tuesday for his first face-to-face meeting since the company announced the Oshawa plant closure in November. They will discuss plans the company has to hire at a Markham, Ont., facility and to expand a call centre it operates in Oshawa, he said.

Ford's recent comments on GM are a change in tone from the days and weeks after the plant closure was announced when he said politicians and union leaders who were promising to fight the company's plan were "grand standing."

Dias had criticized Ford for his initial response to the news, saying in December that if the premier wasn't prepared to fight for workers' jobs he should "just be quiet and get out of the way."

In addition to the Oshawa plant, GM announced that it was planning to close four other plants in the United States and two overseas by the end of 2019 as part of a global restructuring that will see the company cut costs and focus more on autonomous and electric vehicles.

General Motors recently announced an improvement to its financial forecast for the year ahead but has unequivocally stated that its decision regarding the Oshawa plant is final.