Breaking with decades of US policy, Trump said on Twitter that a weaker dollar would help American firms compete.

“As your President, one would think that I would be thrilled with our very strong dollar. I am not!” he said.

“The Fed’s high-interest rate level, in comparison to other countries, is keeping the dollar high, making it more difficult for our great manufacturers like Caterpillar, Boeing… John Deere, our car companies, & others, to compete on a level playing field.”

The latest outburst comes amid the escalating trade war with China – days after the US Treasury labelled Beijing a currency manipulator for allowing the yuan to depreciate slightly in the face of new US tariffs – and the comments appeared to edge closer to a currency war.

For decades, US administrations of both parties have steadfastly advocated keeping the dollar strong since that provides stability and can hold down inflation by making imported goods less expensive.

But a strong currency also makes US exports more expensive. Caterpillar has lowered earnings targets for this year, given declining sales in China amid the exchange of tariffs.

Trump has been relentlessly pressuring the Fed to cut interest rates in almost daily tweets.

“With substantial Fed Cuts (there is no inflation) … the dollar will make it possible for our companies to win against any competition,” he said.

But the US central bankers “have called it wrong at every step of the way.”