Trump has justified tariffs on goods from Canada, the top U.S. export market, by accusing it of failing to stop the cross-border flow of fentanyl, even though U.S. government data shows Canada accounts for only 1% of the fentanyl that enters the United States.

President Trump's threat, posted in the early hours Thursday on his social media network, is the latest way he has sought to use his trade war to coerce countries on unrelated issues and is a swing from the ambivalence he has expressed about other countries making such a move.

The US will hit scores of nations across the world with steep tariffs starting from August 7. Trump also raised duties on Canada from 25% to 35%, with those levies coming into effect on Friday. DW has the latest.