Trump signed proclamations that raised the tariff rate on aluminium imports to 25 per cent, from the previous 10 per cent that he imposed in 2018 to aid the struggling sector.
His action reinstates a 25 per cent tariff on millions of tons of steel imports and aluminum imports that had been entering the US duty free under quota deals, exemptions and thousands of product exclusions.
Earlier, Australia's prime minister Anthony Albanese said the US president was considering an exemption for Australian steel and aluminium products following a phone call between the two leaders on Tuesday morning Australian time.
"We agreed on wording to say publicly, which is that the US president agreed that an exemption was under consideration for in the interests of both of our countries," Mr Albanese said in Canberra.
But there was no specific mention of Australia, or an exemption, as news began to break that the proclamations had been signed.
The proclamations were extensions of Trump's 2018 Section 232 national security tariffs to protect steel and aluminum makers.
A White House official said the exemptions had eroded the effectiveness of these measures.
Trump also will impose a new North American standard requiring steel imports to be "melted and poured" and aluminum to be "smelted and cast" in the region to curb imports of minimally processed Chinese steel into the US
The order also targets downstream steel products that use imported steel for tariffs.
Trump's trade adviser Peter Navarro said the measures would help US steel and aluminum producers and shore up America's economic and national security.
"The steel and aluminum tariffs 2.0 will put an end to foreign dumping, boost domestic production and secure our steel and aluminum industries as the backbone and pillar industries of America's economic and national security," he told reporters.
"This isn't just about trade. It's about ensuring that America never has to rely on foreign nations for critical industries like steel and aluminum."
Trump first broached the steel and aluminum action on Sunday, adding that he would also announce a further set of reciprocal tariffs later in the week, drawing warnings of retaliation from trade partners.
Shares in US steel and aluminium makers rose while shares in European and Asian steelmakers fell.
The largest sources of US steel imports are Brazil, Canada and Mexico, followed by South Korea and Vietnam, according to government and American Iron and Steel Institute data.
Meanwhile, Canada, whose extensive hydropower resources aid its metal production, accounted for 79 per cent of US primary aluminium imports in the first 11 months of 2024.
During his first four-year term from 2017, Trump imposed tariffs of 25 per cent on steel and 10 per cent on aluminium.
But he later granted several countries exemptions including Australia, Brazil, Canada and Mexico and his successor Joe Biden later negotiated duty-free quota deals with the United Kingdom, Japan and the EU.
Australia, a strategic US ally, has been making representations on aluminium and steel for months.
The European Commission said it saw no justification for the imposition of tariffs: "We will react to protect the interests of European businesses, workers and consumers."
Commission President Ursula von der Leyen will meet US Vice President JD Vance in Paris on Tuesday during an AI summit.
US steel mill capacity usage jumped above 80 per cent in 2019 after Trump's initial tariffs but has since fallen as China's global dominance - unaffected by its exclusion by tariffs from the US market - has pushed down prices.
Kevin Dempsey, head of the American Iron and Steel Institute, said it would work with Trump "to implement a robust and reinvigorated trade agenda to address the many foreign market-distorting policies and practices that create an unlevel playing field for American steelmakers".
