Canada's autoworkers' union Unifor and General Motors Co made little progress resolving the key issue of new investment in contract talks late on Sunday, the union's president said, just over 24 hours ahead of a strike deadline.

The automaker and the union representing its Canadian manufacturing workers have been divided over union demands that GM commit to building new vehicle models at its Oshawa, Ont., plant.

"There's a hell of a lot of work to do and not a lot of time with which to do it," said Unifor National President Jerry Dias in an interview.

Asked whether the two sides were discussing a new product for GM's Oshawa assembly, Dias said: "They understand that they have to do something, but we're not really talking about anything specific, which is problematic."

Dias said the union has not yet received a contract proposal from GM, but he remains confident the automaker will eventually offer a product. He said the union will not extend its strike deadline. GM declined to comment.

A four-year contract covering the workers of GM, Fiat Chrysler Automobiles and Ford Motor Co in the province of Ontario expires on Monday.

The union chose GM as its strike target for contract talks, with any deal setting the pattern for the next round of talks with the other manufacturers. Contract talks could save 2,500 jobs at GM's Oshawa car assembly or take the plant one step closer to closure.

Industry struggling in Canada

There are no obvious products that would go into GM's Oshawa plant and the automaker has previously said it will only make future product decisions after a labour deal. Pensions and wages are also on the table.

Dias said no specific model has been discussed so far, but rejected the argument that GM has no product to allocate to the Oshawa plant.

Unifor is determined to get GM to commit to making new vehicle models at the Oshawa plant. (Chris Young/Canadian Press)

"There has been a straight migration of products from north to south. There's no reason why there can't be a migration from south to north," he said.

Canada has been struggling to get new investment from automakers in its once-thriving car industry, losing out to the southern United States and lower-cost Mexico. Between 2001 and 2013, some 14,300 jobs were lost in vehicle manufacturing in Canada, according to the Automotive Policy Research Centre in Hamilton, Ont.

Still, the union has said it will not sign without a vehicle commitment, calling it pivotal for the future of Canada's auto industry.

The strike would affect workers at GM's Oshawa vehicle assembly and St. Catharines, Ont., powertrain plants.

It could also have serious implications for parts makers, including Lakeside Plastics in Woodstock, Ont., which supplies parts for General Motors. The company told the Windsor Star a strike could force layoffs at the parts maker, which employs 400 people.

GM was already on the verge of shutting one of two assembly lines at its Oshawa plant, with several vehicles either produced in another country or expected to move in 2017.

Strike effectiveness depends on CAMI solidarity

A strike at Oshawa, which assembles the Chevrolet Impala, Buick Regal and Cadillac XTS sedans as well as some other overflow work, would not cause much hardship for GM.

But if workers at its Ingersoll, Ont., CAMI plant support the strike and refuse to install engines and transmissions diverted from U.S. or Mexican plants, it would be more damaging for GM.

The CAMI plant assembles GM's strong-selling Chevrolet Equinox and the GMC Terrain. Workers there have the same union but a different contract.

The U.S. United Auto Workers has said it will support its Canadian counterpart, but declined to say whether it would refuse work at American GM plants in the event of a strike north of the border.