Business groups, economists and even some Republicans cautioned that new tariffs on goods from Canada, Mexico and China could undercut U.S. industry and the economy.

What to know as President Donald Trump imposes steep new tariffs on imports from Canada, Mexico and China, prompting retaliation and countermeasures.

Wall Street opened lower after Trump's tariffs on Mexico, Canada and China, sparking fears of trade wars that'll slow economies and ignite inflation.