US President Donald Trump said on Sunday he will introduce new 25-percent tariffs on all steel and aluminum imports into the United States, on top of existing metals duties, in another major escalation of his trade policy overhaul.

Trump, speaking to reporters on Air Force One on his way to the NFL Super Bowl in New Orleans, said he will announce the new metals tariffs on Monday.

He also said he will announce reciprocal tariffs on Tuesday or Wednesday, to take effect almost immediately, applying them to all countries and matching the tariff rates levied by each country.

"And very simply, it's, if they charge us, we charge them," Trump said of the reciprocal tariff plan.

The largest sources of US steel imports are Canada, Brazil and Mexico, followed by South Korea and Vietnam, according to government and American Iron and Steel Institute data.

Trump also said that while the US government would allow Japan's Nippon Steel to invest in US Steel, it would not allow this to become a majority stake.

"Tariffs are going to make it very successful again, and I think it has good management," Trump said of US Steel.

Trump, during his first term, imposed tariffs of 25 percent on steel and 10 percent on aluminium, but later granted several trading partners duty-free exemptions, including Canada, Mexico and Brazil.

Former president Joe Biden later negotiated duty-free quota arrangements with Britain, the European Union and Japan. It was not immediately clear from Trump's announcement what would happen to those exemptions and quota arrangements.

Steel mill capacity usage jumped to levels above 80 percent in 2019 after Trump's initial tariffs, but has fallen since then as China's global dominance of the sector has pushed down steel prices.

Shares of steelmakers in Asia mostly fell on Monday, save for those with operations in the United States. The US dollar rose and US Treasury yields ticked higher. (Agencies)