President Trump on Monday formally installed John F. Kelly, a retired four-star Marine general, as his White House chief of staff, in a bid to bring more discipline to a West Wing in turmoil. 

Kelly, whose work Trump has profusely praised as secretary of homeland security, takes over for Reince Priebus, the former chairman of the Republican National Committee, whose departure from the West Wing had been rumored for months.

Trump said he has “no doubt” that Kelly — whose appointment was announced via Twitter on Friday — will do a “spectacular job” in his new role.

“What he’s done in terms of homeland security is record-shattering,” Trump said, saying Kelly had achieved “tremendous results” in “a controversial situation,” a reference, among other things, to the administration’s implementation of a temporary travel ban on refugees and residents of several majority-Muslim countries and its more aggressive enforcement of immigration laws.

“We look forward, if it’s possible, to an even better job as chief of staff,” Trump said.

“I'll try, sir,” Kelly responded.

Kelly takes over at a time when Trump faces historically low approval ratings, a stalled legislative agenda and an escalating investigation into Russia's alleged interference in the 2016 election.

Asked by a reporter what will be different under Kelly, Trump said his administration “has done very well” and set “lots of records.”

He said that “the stock market is the highest it’s ever been,” that the unemployment rate is “the lowest it has been in 17 years” and that business confidence is high.

“We’re doing very well. We have a tremendous base,” Trump said. “The country is optimistic. And I think the general will just add to it.”

Following the swearing-in, Trump convened his first Cabinet meeting with Kelly as chief of staff.

The gathering marked the first known face-to-face encounter between Trump and Attorney General Jeff Sessions, since Trump has started publicly voicing his disappointment in the attorney general's performance, calling him “beleaguered” among other things.

Trump made no mention of Sessions, who sat across the table from him, during the brief time the press was allowed in the room.

Asked by a reporter about North Korea’s continued testing of ballistic missiles, Trump said: “We’ll handle North Korea. We’ll be able to handle North Korea. It will be handled. We handle everything.”

The president also continued to heap praise on Kelly, predicting he will go down in history as one of the great White House chiefs of staff.