A top trade adviser to US President Donald Trump says a process will be in place for businesses to get exemptions from the White House plan to place steep tariffs on steel and aluminium, offering the first indication a tariff hike could be less broad than first thought.

Peter Navarro, director of the White House National Trade Council, said countries will not be excluded from the tariffs because that would become a slippery slope, but there will be a mechanism for corporate exemptions in some cases.

“There will be an exemption procedure for particular cases where we need to have exemptions, so that business can move forward,” Mr Navarro said on CNN’s State of the Union program.

The scenario of possible exceptions came after Mr Trump’s surprise announcement on Thursday and subsequent aggressive business lobbying against the tariffs, an outcry from US trading partners, including Australia, and criticism from fellow Republicans.

Mr Trump has spoken to world leaders about the planned tariff hikes but has given no indication he would allow exemptions, Commerce Secretary Wilbur Ross said on Sunday.

Mr Navarro did not elaborate on the exemption procedure and the White House did not immediately return a request for comment.

Peter Navarro says there be will some exemptions “so that business can move forward”. Photo: Twitter

Mr Navarro and Mr Ross, who have advocated stronger trade policies to reduce US trade imbalances, went on Sunday US television news shows to try to contain the global fallout from Mr Trump’s announcement.

The president said the US would impose duties of 25 per cent on imported steel and 10 per cent on aluminium to protect domestic producers. The plan stunned US trading partners, alarmed American industry leaders and roiled stock markets.

Josh Bolten, chief executive officer of the influential Business Roundtable, told Fox News Sunday program the tariffs would cause “huge damage” across the economy without affecting China.

A frequent target of Mr Trump’s criticism on trade, China accounts for 2 per cent of US steel imports.

A number of Republicans, including congressional leaders, urged Mr Trump to hold back on the tariffs.

At North American trade talks in Mexico City, Republican Representative Kevin Brady, the top US lawmaker on trade policy, said the administration should exempt current aluminium and steel contracts to avoid business uncertainty.

Numerous world leaders and ministers have been in touch with Mr Trump and US officials including Mr Ross, suggesting an intensive behind-the-scenes effort to change the president’s mind, the commerce secretary said.

Mr Ross said the proposed tariffs represent a fraction of 1 per cent of the US economy so they would not have a great impact.

The commerce secretary dismissed European Union threats of retaliatory tariffs on flagship American products, including Harley Davidson motorcycles, bourbon and Levi’s jeans, calling the $US3 billion ($3.87 billion) in affected goods a “pretty trivial” amount.

Shadow Treasurer Chris Bowen said even if Australia were to get an exemption, there would still be other consequences such as affected companies dumping their steel here.

“It’s lose, lose, lose,” he told ABC Radio.

“I think we should look at all options in the national interest.”

-AAP