President Donald Trump has announced that his chief of staff John Kelly will leave his job by the end of the year.
There have been persistent reports for several days that Mr Kelly was under pressure to go.
Some reports said that the retired Marine Corps general's relationship with Mr Trump had deteriorated.
But Mr Trump described Mr Kelly as a "great guy" and said a replacement would be named "over the next day or two".
"He's been with me almost two years now, between two positions," Mr Trump said. "I appreciate his service very much."
In total, 28 people have resigned or been fired from the White House during Mr Trump's administration.
Last month Reuters news agency quoted a source as saying that Vice-President Mike Pence's chief of staff Nick Ayers was a possible contender for the chief of staff role.
Earlier this year Mr Kelly was forced to deny that he had called Mr Trump an "idiot" after the quote was included in a book about Mr Trump by the veteran investigative journalist Bob Woodward.
Mr Kelly is said to have used the description repeatedly and also allegedly said that "it's pointless to try to convince him of anything".
Mr Trump initially nominated Mr Kelly to oversee Homeland Security before promoting him to chief of staff last July, replacing Reince Priebus.
On Saturday, the president also announced that his highest-ranking military officer, Gen Joe Dunford, would be retiring as chairman of the Joint Chiefs of Staff.
He tweeted to say Gen Mark Milley, the current Chief of Staff of the US Army, would replace Gen Dunford.