GM Canada has been hit with its first assembly plant strike in more than two decades as uncertainty on North American trade negotiations loom over contract talks with workers at its CAMI operation in Ingersoll.

The 2,500 members of Unifor local 88 walked out Sunday at 10:59 p.m. as the two sides failed to reach agreements on plant operations, economic issues, and especially job security.

Local 88 president Dan Borthwick, reached by phone on the picket line, said the union is pushing to have the plant designated the lead producer of GM's Chevrolet Equinox to ensure jobs aren't shifted to Mexico.

He said the issue has become more pressing after GM shifted production of its Terrain small SUV from the plant to Mexico earlier this year at a loss of more than 400 jobs.

"We're done with that. We need some job security and commitment," said Borthwick.

"GM just has to get around their corporate greed. They need to start sharing the $12 billion they make a year."

The company said in a statement that it's disappointed the two sides couldn't reach a deal, but said both sides have made progress on issues in recent weeks and encouraged Unifor to resume negotiations.

GM said it committed $800 million in 2015 to prepare the CAMI plant for the latest Equinox model, but with some production of the vehicle already happening in Mexico, Borthwick said he wasn't reassured by the investment.

"The $800 million was spent when the Terrain was here, so there's no guarantees."

The shifting of work to Mexico is a key issue for the ongoing North American Free Trade Agreement negotiations, and creates significant complications for automaker labour negotiations, said Brendan Sweeney, project manager at McMaster University's Automotive Policy Research Centre.

"There's so much uncertainty. How can they make these commitments today when obviously NAFTA is being renegotiated? I don't know how they can do that; they're kind of hamstrung."

Sweeney said GM and other automakers were able to reach contract agreements last year, with Unifor securing large investments from GM in its Canadian operations including its assembly plant in Oshawa, Ont.

But workers at the CAMI plant operate under a different contract from other GM employees, and their renewal negotiations have come at a tricky time as automakers face uncertainty on key policies like how many cars they'll be able to import to the U.S. from Canada and Mexico, and whether those vehicles will face tariffs.

"Any movement one way or another on those issues will impact what companies do. But the companies won't do that stuff until they know. So it's just crappy timing to be bargaining," said Sweeney.

Unifor president Jerry Dias said CAMI is a "poster child" for what's wrong with NAFTA, where GM shifted production from one of the most productive plants in the world to Mexico to pay workers $2 an hour.

He said trade negotiations will have to address the low wages for workers in Mexico, where automakers have opened eight assembly plants with more on the way after closing four in Canada and 10 in the U.S.

"NAFTA in itself is a complete and utter disaster," said Dias. "Workers from all three countries got screwed. Canada and the U.S., we lost our jobs, and Mexico they never gained as a result of it."

The strike is the first assembly plant strike in Canada since GM workers walked off the job in 1996, with Dias saying union members are fed up with the continuing job losses.

"The fact is we've just had enough, everyone's just had enough."