US President Donald Trump's top economic adviser Gary Cohn is resigning, the White House has said.

It is the latest in a series of high-profile departures from President Trump's team.

There has been speculation that Mr Cohn, a supporter of free trade, was angered by Mr Trump's plans to impose tariffs on aluminium and steel imports.

The 57-year-old former president of the Goldman Sachs bank had helped Mr Trump push through his sweeping tax reforms late last year.

Mr Cohn wasn't specific about the reasons, saying in a statement it had been "an honour to serve my country and enact pro-growth economic policies to benefit the American people, in particular the passage of historic tax reform".

Once that mission had been achieved, a number of differences may have prompted the departure, including the possible looming trade tariff war and his differences on that issue with trade adviser Peter Navarro and Commerce Secretary Wilbur Ross.

Mr Cohn had reportedly set up a meeting between Mr Trump and business executives who opposed the tariffs move.

But Mr Trump pulled out of that meeting and on Tuesday reportedly asked Mr Cohn in the Oval Office to back the tariffs publicly. Mr Cohn did not answer, sources told Bloomberg.

In August last year, Mr Cohn had also criticised Mr Trump over his reaction to a far-right rally in Charlottesville, Virginia, saying the administration "can and must do better".

He was reported to have drafted a resignation letter after the event.

An official said: "For several weeks Gary had been discussing with the president that it was nearing time for him to transition out."

In a statement, Mr Trump said: "Gary... did a superb job in driving our agenda, helping to deliver historic tax cuts and reforms and unleashing the American economy once again.

"He is a rare talent and I thank him for his dedicated service to the American people."