Acting White House chief of staff Mick Mulvaney drew a stark contrast between his leadership style and that of his predecessor's, the retired US Marine Corps Gen. John Kelly.

Mulvaney initially praised Kelly's storied tenure in the Marine Corps and described him as a "true, great American."

But Mulvaney later said there was "one thing" Kelly did that undermined the Trump administration.

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Acting White House chief of staff Mick Mulvaney drew a stark contrast between his leadership style and that of his predecessor's, the retired US Marine Corps Gen. John Kelly, during a panel at the Milken Institute's 2019 Global Conference on Tuesday.

Mulvaney initially praised Kelly's storied tenure in the Marine Corps and called him a "true, great American." But Mulvaney later said there was "one thing" Kelly did that undermined the Trump administration.

"[Kelly] openly let everybody know who worked for him that he hated his job," Mulvaney said. "Every single day, he told people how much he hated his job. Imagine what that would do for the morale in your operation. You can imagine what it did for our morale."

"That was a mistake," Mulvaney added. "And once you fix that, I think we've been able to fix that, things have gotten dramatically better very, very quickly."

The White House did not immediately respond to requests for comment on Mulvaney's remarks about Kelly on Tuesday night.

A representative at the Department of Defense where Kelly previously worked as Homeland Security secretary declined to comment.

Mulvaney gave a glowing assessment of the current mood in the White House and said he did not believe there would be major changes to Trump's cabinet in the near future.

"I think people like working in the White house," Mulvaney said. "They love working for this president and we're having some success. So it's a fun place to work."

Read more: 'God punished me, I guess': John Kelly riffs on his transition from Homeland Security secretary to Trump's chief of staff

In 2017, Kelly took office at a time when the White House was rife with turmoil and infighting. His status as a career US Marine was seen as a potential asset to President Donald Trump, who was at the center of the chaos in the early days of his administration.

As Kelly took over, the White House's scandals did not stop and reports of infighting continued to surface. Kelly was reported to have signaled his displeasure serving in the Trump White House and often referred to him as "an idiot," according to former officials cited by NBC News.

Kelly denied disparaging Trump and described the characterization as "total BS," according to an NBC News report in 2018.

Kelly resigned in December 2018 and was replaced by Mulvaney, who had been working as the director of the Office of Management and Budget.

Mulvaney appears to be taking a different approach to the inner workings of the White House. Instead of fending off White House senior advisers Jared Kushner and Ivanka Trump, Mulvaney has curried favor with members of Trump's family, according to a New York Times report published in January.

Mulvaney has also advised Trump to trust his impulses, The Times reported. Because of that, the Republican Sen. Richard Shelby of Alabama called Mulvaney "the most dangerous man" in Washington, according to three people familiar with his comments who were cited by the newspaper.