WASHINGTON (Reuters) - 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.

President Trump has threatened to impose tariffs on Canada over drug trafficking, equating it with Mexico. U.S. government reports do not support the claim.

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.

The Trump administration is following through on its promise to impose 25% tariffs on goods imported from Mexico and Canada and raise tariffs on Chinese goods on Saturday.

Amid warnings of price increases, Canada moved quickly to retaliate, China said it had planned countermeasures and Mexico said it would soon unveil its response.

U.S. President Donald Trump on Saturday ordered 25% tariffs on Canadian and Mexican imports and 10% on goods from China starting on Tuesday and declared that they would remain in place until a national emergency over the drug fentanyl and illegal immigration to the U.

Trump knows the United States has more leverage over its neighbors than they do over his country. But exploiting that position of strength could cause a historic rupture.

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.

The move likely will trigger retaliation and risk igniting a trade war that could cause broad economic disruption for all countries involved.

WASHINGTON— President Donald Trump on Saturday signed an order to impose stiff tariffs on imports from Mexico, Canada and China, drawing swift retaliation and an undeniable sense of betrayal from the country's North American neighbors as a trade war erupted among the longtime allies.