Trudeau, who spent the weekend in London meeting with European leaders, has vowed to retaliate should Trump follow through on his threat of hitting Canada with tariffs. Last month, he announced Canada would hit back by imposing 25 per cent tariffs on $155-billion worth of U.S. goods, but shelved those plans once an agreement to delay was reached.

Once the tariffs start, gas prices could shoot up 15 cents a gallon or more at the pump relatively soon, according to a top oil and gas expert.