Mexico has supplanted China as the main source of goods, but imports keep climbing.

The president-elect said that he would impose the across-the-board tariffs on Day 1 and that they would stay in place until Canada, Mexico and China halted the flow of drugs and migrants.

Mexico and Canada are the United States’ top two trading partners, accounting for nearly 30% of trade volumes.

Economists worry that Trump's tariff plan will raise the prices of a range of imported goods, from cars to electronics.

The tariffs, if implemented, could dramatically raise prices for American consumers on everything from gas to automobiles to agricultural products.

Trump, who takes office on Jan. 20, said he would impose a 25% tariff on imports from Canada and Mexico until they clamped down on drugs, particularly fentanyl, and migrants crossing the border, in a move that would appear to violate a free-trade deal.

Chinese firms are on edge and so are some of their US partners. Markets are relatively muted, though the yuan is down.

After President-elect Donald Trump takes the oath of office next month, U.S.-China relations are poised to be one of the greatest foreign policy challenges for the new administration.

By Joe Cash BEIJING (Reuters) -China attacked U.S. President-elect Donald Trump's pledge to slap additional tariffs on Chinese goods over fentanyl flows, saying his incoming administration was pushing the blame for America's opioid crisis onto China.