US President Donald Trump has unveiled sweeping new import tariffs, including 100 per cent duties on patented drugs and 25 per cent levies on heavy-duty trucks starting next week, triggering fresh trade uncertainty after a period of comparative calm.

The latest salvo, which Trump said was to protect the US manufacturing industry and national security, follows wide-ranging duties on trading partners of up to 50 per cent and other targeted levies on imported products such as steel and autos.

Trump's announcement on Friday on Truth Social of the steep duties that go into effect on Wednesday shattered a relative lull in his tariff assault on global trading partners, throwing new obstacles at businesses already struggling with disrupted supply chains, soaring costs and consumer uncertainty.

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