"When a country (the US) is losing many billions of dollars on trade with virtually every country it does business with, trade wars are good, and easy to win," he tweeted on Friday night.

 

"Example, when we are down $100 billion with a certain country and they get cute, don't trade anymore-we win big. It's easy!," he added.

 

The President's announcement on Thursday that he will order tariffs of 25 per cent and 10 per cent, respectively, on imported steel and aluminium, spurred a 420-point drop on the New York Stock Exchange and expressions of alarm.

 

Some of the sharpest criticism of the planned tariffs came from Trump's fellow Republicans, most of them ardent free-traders.

 

"Kooky 18th century protectionism will jack up prices on American families - and will prompt retaliation from other countries," Senator Ben Sasse said in a statement.

 

"Make no mistake: If the President goes through with this, it will kill American jobs - that's what every trade war ultimately does," the Nebraska Republican said.

 

House Speaker Paul Ryan said that US workers and firms could suffer from "unintended consequences" if the tariffs were imposed, while European Commission chairman Jean-Claude Juncker was one of several international leaders threatening retaliation for the levies.

 

Roberto Azevedo, the Director-General of the World Trade Organization (WTO), broke with his usual practice by commenting publicly on Trump's announcement.

 

"The WTO is clearly concerned at the announcement of US plans for tariffs on steel and aluminium. The potential for escalation is real, as we have seen from the initial responses of others. A trade war is in no one's interests," Azevedo said.

 

Asked on Friday about the negative reception to Trump's tariff idea, White House spokeswoman Sarah Sanders said that the President was not concerned and that he remained "pretty committed" to moving this forward.

 

Paradoxically, Trump's proposal got a much warmer response from some Democrats, such as Ohio Senator Sherrod Brown, who described the tariffs as "long overdue" action to aid steelworkers in his state.

 

Trump also won plaudits from the country's largest labour federation.

 

"For years, we have called attention to the predatory practices of some steel exporting countries," AFL-CIO President Richard Trumka said. "This is a great first step toward addressing trade cheating."

 

The President's decision was not unanimously popular within his own administration.

 

Gary D. Cohn, the director of the National Economic Council, "threatened to resign if the White House followed through with stiff and sweeping tariffs, according to people who have spoken with him in recent days".