U.S. tariffs against Canada could come in two steps, with the first blow coming as early as Saturday if Ottawa can't show it has shut its borders to illegal immigration

The man U.S. President Donald Trump has chosen to oversee his tariff agenda says hitting Canada with 25 per cent across-the-board duties would be an emergency measure to achieve border security — and could be followed by more tariffs in the future.

Mr. Trump and the White House have repeatedly said they intend to impose tariffs on Canada and Mexico on Saturday, prompting a renewed effort by the Canadian government to seek relief that included a multiday visit to Washington by Foreign Minister Mélanie Joly, who met Wednesday with Secretary of State Marco Rubio.