Donald Trump suspects his defense secretary, General Jim Mattis, might be a Democrat and “could be” heading for the exit.

Trump was responding to a specific question from journalist Lesley Stahl, for an interview for CBS News’ 60 Minutes, about whether Mattis was “going to leave”.

“Well, I don’t know,” the president said. “He hasn’t told me that.”

“Do you want him to?” Stahl pressed.

“I have a very good relationship with him,” Trump said. “I had lunch with him two days ago. I have a very good relationship with him.

“It could be that he is. I think he’s sort of a Democrat, if you want to know the truth. But General Mattis is a good guy. We get along very well. He may leave. I mean, at some point, everybody leaves. Everybody. People leave. That’s Washington.”

Mattis was a US Marines commander in the 2003 invasion of Iraq and was elevated under George W Bush to command the United States Joint Forces Command. Under Barack Obama, he became commander of US Central Command.

The defense department did not immediately respond to a request for comment.

In its first two years, the Trump administration has witnessed an unprecedented flow of high-profile departures. This week, UN ambassador Nikki Haley announced she was stepping down.

In a book published last month, journalist Bob Woodward depicted Mattis as directly ignoring an expressed desire by Trump to assassinate the Syrian president, Bashar al-Assad, and comparing Trump’s understanding of tensions on the Korean peninsula to that of “a fifth- or sixth-grader”.

Mattis denied making such statements.

The defense secretary is scheduled to embark for Vietnam on Tuesday in a trip that originally included a Beijing agenda, since canceled.