Canadian and Chinese officials say they were already helping reduce fentanyl smuggling. Prime Minister Justin Trudeau said fentanyl crossing the northern border is "near zero."

The president said the flow of the illicit opioid is one of the reasons for imposing tariffs on trading partners.

China will impose additional tariffs of up to 15% on some U.S. goods, its government said, while Canada vowed tariffs of up to 25% after new U.S. tariffs on both countries took effect.