President Donald Trump said the US will put a 35% tariff on some imports from Canada, escalating the tensions between two countries that have impaired one of the world’s largest trading relationships.

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.

After Canada failed to strike a trade deal with Washington, the president raised tariffs on some Canadian exports this week.