US President Donald Trump has announced steep tariffs on auto imports and parts, provoking threats of retaliation from trading partners ahead of further promised trade levies next week.

As Asian markets opened Thursday, shares in carmakers were down sharply, and Japan's Prime Minister Shigeru Ishiba said his government was "considering all kinds of countermeasures."

"What we're going to be doing is a 25 percent tariff on all cars that are not made in the United States," Trump said, as he signed the order in the Oval Office.

The move takes effect at 12:01am eastern time on April 3 and impacts foreign-made cars and light trucks. Key automobile parts will also be hit within the month.

Canadian Prime Minister Mark Carney branded Trump's tariffs a a "direct attack" on his country's workers. He said that the cabinet would meet Thursday to discuss retaliation.

Peter Navarro, Trump's senior counselor for trade and manufacturing, in a briefing after Trump's announcement blasted "foreign trade cheaters" who he said turned America's once-bustling manufacturing sector into a "lower wage assembly operation for foreign parts."

"That threatens our national security because........

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