U.S. tariffs on Canada have put experts at odds over how appropriate the action was, particularly given the unaddressed demand side of the fentanyl epidemic.

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."

U.S. President Donald Trump's increased tariffs on steel and aluminum imports took effect on Wednesday as prior exemptions, duty free quotas and product exclusions expired, as his campaign to reorder global trade norms in favor of the U.