"They have declared war on Canada," Unifor union president Jerry Dias.

General Motors has reportedly threatened to shift Chevrolet Equinox production to Mexico in response to a lengthy strike at a Canadian factory.

Workers at GM's CAMI factory in Ingersoll, Ontario, walked out a month ago, interrupting production of the company's best-selling crossover. The Equinox is also the fastest-growing model in Chevy's lineup, achieving an 80-percent jump in deliveries last month and more than 22 percent in the first nine months of the year.

GM already builds the Equinox at two different factories in Mexico. The Canadian union, known as Unifor, has demanded that Ingersoll serve as the primary production location for North America, however.

"GM just told us today that they are going to ramp up production in Mexico," Unifor president Jerry Dias told Reuters. "They have declared war on Canada."

A separate source told Reuters the company still faces an uncertain path as it attempts to determine if key suppliers can accommodate a quick shift to alternative production sites.

The walkout aligns with a broader battle over NAFTA, as government officials from the US, Canada and Mexico continue to negotiate over changes to the trade pact.