President Donald Trump has named General John Kelly, who currently heads the Department of Homeland Security, as his next chief of staff. The announcement, made on Twitter on Friday afternoon, removes Reince Priebus from the role.
The embattled former chief of staff had faced pressure since being named as a possible leaker by Mr Trump's newly appointed director of communication. Mr Priebus told CNN he resigned on Thursday after talking with Mr Trump.
The president wanted to go in a different direction, he told CNN's Wolf Blitzer, adding that he thought Gen Kelly was a brilliant pick.
Anthony Scaramucci, who was appointed communications director one week ago, had accused Mr Priebus - a Republican Party stalwart - of leaking to the press. He also phoned a reporter to unleash a profanity-filled rant against Mr Priebus, whom he called a paranoid schizophrenic.
General Kelly is a retired general who has become the face of border security. In a series of tweets just before 17:00 (22:00 GMT) on Friday, the president praised the former Marine Corp general as a great American and a great leader.
John has done a spectacular job at Homeland Security. He has been a true star of my administration, said the president. He will start work on Monday, a White House spokesperson says.
Gen Kelly's deputy, Elaine Duke, will become acting head of the Department of Homeland Security.
In a third tweet, President Trump praised the outgoing chief of staff, who had previously worked as the chairman of the Republican National Committee (RNC).
I would like to thank Reince Priebus for his service and dedication to his country. We accomplished a lot together and I am proud of him, he said.
In his previous role as RNC chairman, he acted as a bridge between the Republican nominee and a party establishment that was often uncomfortable with its own presidential standard-bearer.
White House spokeswoman Sarah Sanders said she did not think the administration's relationship with the Republican Party would be affected by Mr Priebus's exit.
I think we've still got a good relationship. We're going to continue working with the party and doing what we came here to do, she said.
House of Representatives Speaker Paul Ryan, a close friend of Mr Priebus and a fellow Republican, said he had served the president and the American people capably and passionately.
He has achieved so much, and he has done it all with class. I could not be more proud to call Reince a dear friend, he said.