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.
In a statement released by the White House, Mr Cohn said it had been "an honour to serve my country".
The 57-year-old former president of the Goldman Sachs bank helped Mr Trump push through his sweeping tax reforms late last year.
However, the two were not believed to be close.
In August 2017, Mr Cohn 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.
"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," Mr Cohn said in his statement.
"I am grateful to the president for giving me this opportunity and wish him and the administration great success in the future."
Does this herald a new direction?
Analysis by Anthony Zurcher, BBC News, Washington
Gary Cohn was a bit of a stranger in a strange land. He was a Democrat in a Republican White House; an economic globalist working for a president who campaigned on economic nationalism. Now, it seems, Donald Trump's protectionist bent has pushed the top administration economic adviser to the exit.
This was not an unexpected development. By many accounts, there had been a contentious White House fight over whether to impose sweeping sanctions on US steel and aluminium imports - a tug-of-war that was settled, precipitously, by the president himself last week.
There were the rumours that Mr Cohn was only sticking around to see last year's tax bill over the finish line, after his extreme discomfort following the president's warm words about some of the white nationalist marchers involved in violent clashes in Charlottesville last August.
Mr Cohn was reportedly viewed by many Trump loyalists in the White House as an unwelcome interloper. Some on the outside, particularly in the financial world, welcomed him as a moderating influence - along with son-in-law Jared Kushner and daughter Ivanka.
Now the former is leaving and the latter two seem greatly weakened. All this could mark sharp new direction in White House policy.
The White House said Mr Cohn's exact departure date had yet to be determined.
"For several weeks Gary had been discussing with the president that it was nearing time for him to transition out," an official said.
In a statement, Mr Trump described his outgoing economics adviser as "a rare talent".
"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 said.
"He is a rare talent and I thank him for his dedicated service to the American people."
Mr Trump later tweeted that he would pick Mr Cohn's replacement "soon".
"Many people wanting the job - will choose wisely!" he added.
Possible candidates mooted by US media include White House adviser Peter Navarro and Larry Kudlow, a conservative commentator and 2016 campaign adviser.
Earlier on Tuesday, President Trump tweeted that there was no chaos at the White House but there were "still... some people that I want to change".
The White House has seen a string of senior figures leave since Mr Trump took office.
Last week, one of his closest aides, Hope Hicks, resigned. She was the fourth person to have served as the president's communications chief.
It came a day after she had testified in front of the House Intelligence Committee investigating possible Trump campaign ties to Russia, but White House sources said this was not the reason.
