China's state media warned U.S. President-elect Donald Trump his pledge to slap additional tariffs on Chinese goods over fentanyl flows could drag the world's top two economies into a mutually destructive tariff war.

Mexico said it would slap tit-for-tat tariffs on the US, while China said Trump's finger-pointing "runs completely counter to facts".

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.