U.S. set to unleash tariffs on Canada, Mexico and other countries. Economists are worried.

Experts are expressing concern that steep new U.S. tariffs primed to take effect on March 4, along with planned levies on other trading partners, could fan inflation and slow the nation's growth — an economic malaise known as "stagflation."

President Trump on Thursday said on social media that 25% tariffs on Canada and Mexico, which had been delayed for a month while the sides negotiated, will now roll out next week as scheduled. He also this week announced an additional 10% tariff on imports from China, on top of those already in place, set to kick in next week, while 25% tariffs on steel and aluminum imports are lined up for March 12. Sweeping reciprocal tariffs and levies on automobile imports may be deployed as soon as early April, while Mr. Trump has threatened to hit imports from the European Union with 25% duties. 

Mounting uncertainty about the scale and potential impact of such tariffs, including the "somewhat abrupt and arbitrary way" in which they've been announced, risks throttling spending by consumers and businesses, said Marcus Noland, director of studies at the Peterson Institute for International Economics, a nonpartisan research firm.