The Canadian team working on a trade deal with the United States could walk away from talks in the wake of a U.S. decision to impose a 35% tariff on some goods from Canada, an adviser to Prime Minister Mark Carney said on Friday.

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 tariffs order for countries yet to strike a trade deal with the U.S. went into effect just after midnight on Friday, though most levies aren't due to start until Aug. 7. Why it matters: While countries like Mexico struck trade deal extensions ahead of Trump's deadline,