TORONTO - The head of Unifor says General Motors has declared "war on Canada" by ramping up production of its Equinox SUV in Mexico to do more work currently done in Ontario.

Unifor's national president Jerry Dias says from Washington, D.C., that the Detroit-based automaker's threat during labour negotiations on Wednesday is to a "slap in the face" to Canada and the United States.

The union leader's comments come as Prime Minister Justin Trudeau begins an official visit to Mexico and NAFTA trade negotiations continue in Washington, D.C.

Unifor Local 88 is in its fourth week of a strike at the GM's assembly plant in Ingersoll, Ont., one of three factories that make the Equinox sports utility vehicle.

The Equinox has been the CAMI assembly plant's only vehicle since General Motors moved production of the Terrain SUV to Mexico earlier this year.

Dias says GM's movement of work from the CAMI plant to Mexico is an example of what's wrong with the North American Free Trade Agreement, currently being renegotiated.