The Canadian Auto Workers union said it could serve General Motors with a 24-hour strike notice on Thursday afternoon after saying that GM failed to meet the pattern of a deal the union reached with Ford.

CAW spokeswoman Shannon Devine said there are a few key items missing from GM's latest proposal that their members feel are important.

GM disputed the union's contention that it didn't meet the pattern set by Ford.

"Following extensive meetings and dialogue, General Motors of Canada has delivered a proposal to the CAW that meets pattern on all elements of the Ford agreement," GM spokeswoman Faye Roberts said in a statement.

The union decided to keep working past a midnight Monday strike deadline after reaching a tentative deal with Ford and extending its contracts with GM and Chrysler.

Workers are staying on the job as talks continue, but can go on strike after giving GM and Chrysler 24 hours' notice. The CAW wants the Ford contract to serve as a template for the other two companies.

The union said they're making better progress with Chrysler and they're frustrated with GM.

"We don't yet have an agreement with Chrysler but discussions have been constructive and we are making progress," the union said in a news release. "Chrysler executives seem to be more willing to reach an agreement than they were previously."

Canadian Ford auto workers will vote this weekend on the tentative agreement and the union said results of the vote will be released on Sunday night. It cuts wages for new hires and freezes pay for current workers. But it also gives them lump-sum payments to cover inflation and for ratifying the deal.

The auto companies say Canada is the most expensive place in the world to make cars and trucks, and they could move production south if the CAW doesn't cut costs. The CAW represents about 21,000 auto workers in Canada and about 16 percent of auto production in North America.

GM and Chrysler make popular models in Canada that would soon be in short supply if there's a strike. CAW workers also make key engine parts and other components for U.S.-built cars.

Industry analysts say a strike would be felt in U.S. factories in a week or less, and dealers could quickly run short of some models, largely because they haven't built up stocks due to higher demand for cars and trucks in the U.S. In Canada, GM makes the Chevrolet Camaro, Impala and Equinox, along with the Buick Regal, Cadillac XTS and GMC Terrain. Chrysler makes minivans and the Dodge Challenger and Charger, Chrysler 300, and Ram Cargo Van in Canada.

The federal Canadian and Ontario province governments worked in tandem with the U.S. government on auto bailouts in 2009 to maintain Canada's share of North American auto production.