The levy injects fresh turmoil into a strained bilateral relationship and is a setback as Prime Minister Mark Carney negotiates a new economic partnership with the U.S.

President Donald Trump announced a 35% tariff on goods from Canada, one of the USA's largest trading partners and which got hit with a higher rate than threatened for other close allies. The announcement July 10 came amid a flurry of letters going out this week dictating tariff rates for each of more than a dozen countries.