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.

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

Beijing's commerce ministry said tariffs wouldn't 'solve America's own problems.' Investors are taking a wait-and-see approach.