Washington DC - US President Donald Trump announced steep tariffs on auto imports and parts Wednesday, in a move set to fuel tensions with trading partners ahead of further promised levies next week.

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

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

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

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"That threatens our national security because it's eroded our defense and manufacturing industrial base," he said.

He took aim at Germany and Japan for reserving the construction of higher-value parts to their countries.

Since returning to the presidency in January, Trump has imposed fresh tariffs on imports from major US trading partners Canada, Mexico, and China – alongside a 25% duty on steel and aluminum.

The latest levies will be in addition to those already in place for products.

But the White House added that vehicles entering under the US-Mexico-Canada Agreement (USMCA) can qualify for a lower rate depending on their American content.

Similarly, USMCA-compliant auto parts will remain tariff-free as officials establish a process to target their non-US content.