TORONTO -- The massive employee strike that hit General Motors in the U.S. on Monday could migrate to Canada next year if trust is not restored, said Unifor president Jerry Dias.

"Canadian workers and American autoworkers feel the exact same way. They feel betrayed," Dias said in a phone interview.

The union head pointed to plant cutbacks and closures on both sides of the border following pledges to maintain operations, and cited a "credibility problem."

"You would think with great wealth would come incredible loyalty. That just hasn't happened," Dias said, highlighting GM's US$12.7 billion in net profits over the past 18 months.

A strike "may very well" sprout at Canadian plants in 2020, he said. A collective agreement between Unifor and the auto giant is set to expire in September 2020.

More than 49,000 members of the United Auto Workers went on strike against GM in the U.S. Monday, bringing more than 50 factories and parts warehouses to a standstill in the union's first walkout against the no. 1 U.S. automaker in over a decade. Workers left factories and formed picket lines shortly after midnight in the dispute over a new four-year contract.

GM Canada's Oshawa plant will see the vast majority of its 2,600 unionized employees laid off this year, though initial plans to close it were adjusted to save about 300 of those jobs for a parts operation.

Economic Development Minister Vic Fedeli said the Ontario government is in dialogue with GM Canada about the American strike and is monitoring the situation closely.

"We are concerned with the potential impact the labour strike at General Motors in the U.S. may have on the company's operations in Ontario along with our integrated supply chain that delivers parts to GM's facilities in the U.S.," Fedeli said in a statement.

The U.S. union's top negotiator said in a letter to the company that the strike could have been averted had the company made its latest offer sooner.

The letter dated Sunday suggests that the company and union are not as far apart as the rhetoric leading up to the strike had indicated.

But union spokesman Brian Rothenberg said the two sides have come to terms on only two per cent the contract.

"We've got 98 per cent to go," he said Monday.

UAW vice-president Terry Dittes told GM that the company's latest offer might have made it possible to reach an agreement if it had not come just two hours before the union's contract with GM expired on Saturday night.

In the letter to Scott Sandefur, GM's vice-president of labour relations, Dittes wrote that the company waited too long to make the offer. GM issued a statement saying it wants to reach a deal that builds a strong future for workers and the business.

Dittes wrote that there are many important items left in the talks, including wage increases, pay for new hires, job security, profit sharing and treatment of temporary workers.

GM said Sunday it offered pay raises and $7 billion worth of U.S. factory investments resulting in 5,400 new positions, a minority of which would be filled by existing employees. GM would not give a precise number. The company also said it offered higher profit sharing, "nationally leading" health benefits and an $8,000 payment to each worker upon ratification.

Before the talks broke off, GM offered new products to replace work at two of four U.S. factories that it intends to close.

The company pledged to build a new all-electric pickup truck at a factory in Detroit, according to a person who spoke to The Associated Press on condition of anonymity. The person was not authorized to disclose details of the negotiations.

The automaker also offered to open an electric vehicle battery plant in Lordstown, Ohio, where it has a huge factory that has already stopped making cars and will be closed. The new factory would be in addition to a proposal to make electric vehicles for a company called Workhorse, the person said.

It's unclear how many workers the two plants would employ. The closures, especially of the Ohio plant, have become issues in the 2020 presidential campaign. President Donald Trump has consistently criticized the company and demanded that Lordstown be reopened.

Kristin Dziczek, vice-president of labour and industry for the Center for Automotive Research, an industry think-tank , said the letter and resumption of contract talks are encouraging signs. "It makes me think that both sides are probably closer than it might have seemed before," she said.

But both Dziczek and Art Wheaton, an auto industry expert at the Worker Institute at Cornell University, said GM left out key details when it made part of its offer public, and working out those details could make the strike last longer.

"I think GM kind of sabotaged some of the negotiations by going immediately to the public," Wheaton said. "It really distorts the offer."

The strike shut down 33 manufacturing plants in nine states across the U.S., as well as 22 parts-distribution warehouses. It's the first national strike by the union since a two-day walkout in 2007 that had little impact on the company.

With files from The Associated Press