Washington, March 8: US President Donald Trump is set to sign a controversial executive order imposing a hefty 25 per cent import tariff on steel and 10 per cent on aluminium, a move which America's top trading partners said would attract retaliation.

Trump's plan for stiff and sweeping steel and aluminium import tariffs would face retaliation from America's top trading partners, the European Union and China.

More than 100 Republican lawmakers implored President Trump to drop his plan and urged him to focus on unfair trading policies of China. White House trade adviser Peter Navarro told Fox Business late last night that Trump would sign the executive order later in the day. The new tariffs would go into effect in 15-30 days, he said.

"The proclamation will have a clause that does not impose these tariffs immediately on Canada and Mexico, and it's going to give us an opportunity and one of the best guys in this administration, Ambassador Robert Lighthizer the opportunity to negotiate a great deal for this country," Navarro said.

"And if we get that, then all is good with Canada and Mexico," he added. "We're going to open this up for our allies to just see if we can work through this problem," he said.

Yesterday, 107 Republican members of the House of Representatives sent a letter to the president expressing concern about broad tariffs and calling for him to focus any action on unfair trading partners, like China.

"We are writing to express deep concern about the prospect of broad, global tariffs on aluminium and steel imports. Because tariffs are taxes that make US businesses less competitive and US consumers poorer, any tariffs that are imposed should be designed to address specific distortions caused by unfair trade practices in a targeted way while minimising negative consequences on American businesses and consumers," the lawmakers said.

"We support your resolve to address distortions caused by China's unfair practices, and we are committed to acting with you and our trading partners on meaningful and effective action. But we urge you to reconsider the idea of broad tariffs to avoid unintended negative consequences to the US economy and its workers. We are eager to work with you in pursuing a workable, targeted approach that achieves our shared goal," they wrote.

In the letter, Republican lawmakers outlined several recommendations to hold countries accountable without disrupting the flow of fairly traded products that American manufacturers rely on.

However, according to The Wall Street Journal, at the White House yesterday, aides began preparations for the ceremony ushering in a turn in trade policy that could recalibrate relations between the US and its allies and trading partners.

"We are definitely going to end up with these tariffs," Treasury Secretary Steven Mnuchin told Fox Business and "we're going to roll this out very, very quickly."

"The president understands the economy. He understands business. He is looking out for American companies and American workers with trade deals that are just not fair," he said.

The prospect of approaching tariffs has set off furious lobbying from governments around the world, who have tried to sway the administration with offers of friendship and threats of retaliation, The New York Times reported.

Yesterday, the European Union released a list of American-made goods it would penalise if the tariffs went through.

China, which ranks 11 among the largest sources of US steel imports, cautioned that it was prepared to "make an appropriate and necessary response" should the United States impose the tariffs.