President Donald Trump late Thursday threatened a 35% tariff on goods imported from Canada, a dramatic escalation in an on-again, off-again trade war with America’s northern neighbor and one of its most important trading partners.

The president revived his discredited claims about fentanyl entering the U.S. from Canada to justify his latest proposed rate of 35 percent.

Trump has threatened blanket levies of 15% or 20% on most trade partners, and says he will soon announce new tariffs on the EU.