President Donald Trump on Friday tweeted that John F. Kelly would take over as White House chief of staff, replacing the beleaguered Reince Priebus.

Kelly, a retired four-star Marine general, has been serving as Homeland Security secretary.

Priebus, 45, became a target of Trump's ire shortly into his term as White House chief of staff.

Trump has consistently applied pressure on Priebus and reportedly given him various deadlines to get a tumultuous White House in order.

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Reuters, citing a senior White House official, reported Friday that Trump told Priebus two weeks ago that he would replace him as chief of staff. Priebus told CNN in an interview Friday evening that he "formally resigned" Thursday, and that he would help Kelly and the White House staff with a transition over the period of a few weeks starting Monday.

After the announcement Friday, the president offered kind words about Priebus while delivering praise for Kelly.

"Reince is a good man. John Kelly will do a fantastic job. General Kelly has been a star, done an incredible job thus far, respected by everybody," Trump told reporters who had traveled with him Friday on Air Force One. "He's a great great American. Reince is a good man."