US President Donald Trump substantially raised tariffs on steel and aluminium imports on Monday to a flat 25 percent "without exceptions or exemptions", although he agreed to consider an exemption on Australia.

In a telephone call with Australia’s prime minister on Tuesday that took place before the tariff rise, Trump said the US trade surplus with Australia was one of the reasons he was considering an exemption.

“We actually have a surplus," Trump told reporters in the Oval Office about trade with Australia. “It’s one of the only countries which we do. And I told (Albanese) that that’s something that we’ll give great consideration to.”

Australia had an exemption from such tariffs during Trump’s first administration.

Trump signed proclamations raising the US tariff rate on aluminium to 25 percent from his previous 10 percent rate and eliminating country exceptions and quota deals as well as hundreds of thousands of product-specific tariff exclusions for both metals.

Trump also will impose a new North American standard requiring steel imports to be "melted and poured" and aluminium to be "smelted and cast" within the region to curb US imports of minimally-processed metals.

As he signed the order at the White House, Trump said he would follow Monday's action with announcements about reciprocal tariffs on all countries that impose duties on US goods over the next two days, and said he was also looking at tariffs on cars, semiconductor chips and pharmaceuticals.

Asked about threats of retaliation by other countries against his new tariffs, Trump said: "I don't mind."

Monday's tariffs almost immediately drew criticism from Canada, the largest source of steel imports.

Candace Laing, president and CEO of the Canadian Chamber of Commerce, called Trump a destabilising force in the global economy.

Before the proclamations, shares in US steel and aluminium makers jumped, while shares in European and Asian steelmakers fell. The largest sources of US steel imports are Canada, Brazil and Mexico, followed by South Korea and Vietnam, according to government and industry data. (Agencies)