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.

China chose swift retaliation for trade measures in the first Trump administration, but that led to an upward spiral of trade measures and much broader tariffs.

Trump signed an executive order to implement tariffs on Mexico, Canada, and China.He has been threatening the tariffs on the three countries and others for months.Canada and Mexico have vowed to impose retaliatory tariffs against the US.