Trump imposes 25% tariffs on steel, aluminium imports

US President Donald Trump has made good on a promise to slap 25 percent tariffs on steel and aluminium imports, stepping up a long-promised trade war despite warnings from Europe and China.

"Today I'm simplifying our tariffs on steel and aluminium," Trump said in the Oval Office on Monday as he signed executive orders. "It's 25 percent without exceptions or exemptions."

Trump also signalled that he would look at imposing additional tariffs on automobiles, pharmaceuticals and computer chips.

Canada and Mexico — which Trump has already threatened with tariffs — are the biggest steel importers to the United States, according to US trade data.

Brazil and South Korea are also major steel providers.

Australia exemption

The US leader also confirmed that he was considering an exemption for Australia from the steel tariffs.

"We have a (trade) surplus to Australia, one of the few. And the reason is they buy a lot of airplanes. They are rather far away and need lots of airplanes," he said.

Just before Trump signed the documents, Australian Prime Minister Anthony Albanese said an exemption was on the table after speaking with Trump.

"The US president agreed that an exemption was under consideration in the interests of both of our countries," Albanese told reporters after the call.

Trump imposed sweeping tariffs during his 2017-2021 presidency to protect US industries, which he believed faced unfair competition from Asian and European countries.

During the signing, Trump also said he would announce reciprocal tariffs on other countries in the next two days.

Asked about the possibility of other countries retaliating against US tariffs, Trump said: "I don't mind."