China's sharpest pushback on Sunday was over fentanyl, an area where the Biden administration had also been urging Beijing to crack down on shipments.

President Donald Trump's new tariff orders against Canada, Mexico and China all contain clauses suspending a duty-free exemption for low-value shipments below $800 that is widely seen as a loophole that has allowed shipments of fentanyl and its precursor chemicals into 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.