When President Donald Trump imposed new tariffs on Chinese goods Saturday, he homed in on a persistent sore spot in the U.S.-China relationship: Beijing’s role in the global fentanyl trade, which has fueled a deadly opioid crisis in the United States.

The White House says fentanyl smuggled to the U.S. justifies tariffs against Canada, China and Mexico. But fentanyl deaths and smuggling have been dropping fast — and Canada plays almost no role.

China's government on Sunday denounced the Trump administration's imposition of a long-threatened 10% tariff on Chinese imports while leaving the door open for talks with the U.S. that could avoid a deepening conflict.