Mark Carney says Canada will impose tariffs starting September 8 on imports of US steel, electronics and other products.

Negotiations between the U.S. and Canada broke down late Friday and tariffs went into effect early Saturday morning.

Canadian Prime Minister Mark Carney vows to retaliate, says his country recognized that 'America has changed' and that the two countries would 'not return to our old relationship'

Canada would match US tariffs "dollar for dollar", says Prime Minister Mark Carney.