Growth expectations for the U.S. economy are falling as China and Canada announce their next move in the tit-for-tat trade spat with the White House.

Stocks fall sharply Monday, extending declines in late afternoon trade as President Donald Trump affirmed 25% tariffs on imports from Canada and Mexico will take effect. Earlier, stocks felt pressure after a weaker-than-expected February reading for a key manufacturing index.

Consumers in the US could see price hikes within days, an expert has said, adding "the automobile sector, in particular, is likely to see considerable negative consequences".