Top White House economic adviser Gary Cohn, a Wall Street banker who became a key architect of the 2017 tax overhaul and a bulwark against protectionist forces within the Trump Administration, is resigning, the White House has announced.

"It has 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," Cohn said in a statement issued by the White House.

"I am grateful to the President for giving me this opportunity and wish him and the Administration great success in the future."

President Donald Trump earlier denied that his White House is chaotic, but predicted more staff will leave, as allies and observers worry about West Wing brain drain.

Trump's White House has made instability a virtue, but weeks of dysfunction and disarray — and a series of high-profile departures — raised internal fears of an exodus.

Trump maintained that his White House has "tremendous energy," but multiple White House officials said Trump has been pushing anxious aides to stay.

"Everyone wants to work in the White House," Trump said during a joint press conference with Swedish Prime Minister Stefan Löfven. "They all want a piece of the Oval Office."

In a tweet earlier today, Trump sought to portray himself as the architect of some of the changes, writing, "I still have some people that I want to change (always seeking perfection)."

Trump acknowledged that he is a tough boss to work for, saying he enjoys watching his closest aides fight over policy. "I like conflict," he said during the press conference.

But it's a conflict over trade policy that is believed to have provoked the departure of Cohn. Cohn, a former Goldman Sachs banker, has been the strongest West Wing opponent of Trump's plan to place tariffs on steel and aluminum imports.

Cohn mounted an eleventh-hour campaign to swing the President's thinking around, but Trump so far has refused to back down on the proposal, despite opposition from Republicans on Capitol Hill, international allies and many in the business committee.

A person who deals with the administration regularly on economic issues said before the resignation statement that Cohn was expected to leave within a couple of days of the formal tariffs announcement.

- Reuters, AAP, AP