Mattis and Trump
Mattis and Trump Reuters

US President Donald Trump hinted on Sunday that Defense Secretary Jim Mattis "could be" leaving, referring to him as "sort of a Democrat", AFP reports.

Speaking on CBS's "60 Minutes," Trump was asked whether he wanted Mattis to leave.

"It could be that he is. I think he's sort of a Democrat, if you want to know the truth," the President replied, before adding, "But General Mattis is a good guy. We get along very well. He may leave. I mean, at some point, everybody leaves."

Trump said he had lunch with Mattis two days earlier and Mattis, a retired Marine four-star general, had not told him that he was leaving.

The exchange on the Defense Secretary came after Trump alluded to upcoming changes in his cabinet, which last week saw the surprise resignation of Nikki Haley, the US ambassador to the United Nations.

"I'm changing things around. And I'm entitled to. I have people now on standby that will be phenomenal. They'll come into the administration, they'll be phenomenal," Trump told CBS.

"I think we have a great cabinet. There're some people that I'm not happy with. I have some people that I'm not thrilled with. And I have other people that I'm beyond thrilled with," he added.

Mattis is seen as one of the steadiest but also more independent members of Trump's cabinet, and has served as a low-profile counterweight to the President.

There is no knowledge of friction between the two, though veteran journalist Bob Woodward, in his recently published book “Fear”, claimed that Mattis told colleagues “the president acted like — and had the understanding of — a ‘fifth or sixth grader’” in relation to the nuclear standoff with North Korea.

Mattis called the quotes attributed to him “fiction” and the “product of someone’s rich imagination”.

“The contemptuous words about the President attributed to me in Woodward’s book were never uttered by me or in my presence. While I generally enjoy reading fiction, this is a uniquely Washington brand of literature, and his anonymous sources do not lend credibility,” he made clear last month.