Trump's tariffs on Canada, Mexico and China suggest he is willing to risk a global trade war. The main thing that could stop him would be a stock market selloff.

Business groups, economists and even some Republicans cautioned that new tariffs on goods from Canada, Mexico and China could undercut U.S. industry and the economy.

Prime Minister Justin Trudeau set out "far-reaching" tariffs of 25%, affecting 155bn Canadian dollars' worth ($106.6bn; £86bn) of American goods ranging from beer and wine, to household appliances and sporting goods.