The president denied that Mattis had been required to explain to him that North Atlantic Treaty Organisation and other alliances existed to "prevent World War III", a claim made in veteran journalist Bob Woodward's recently published book about the Trump White House.
Speaking to 60 Minutes on CBS Mr Trump said "it could be" that Mr Mattis would not remain in his post for long. "And I think, frankly, China.is a bigger problem", Trump said, while denying that he was trying to divert attention from Russian Federation. I don't want to give trillions and trillions of dollars. "And I know more about it from the standpoint of fairness, that I can tell you". "The problem was, I was getting to know the leaders. I think it's a very unfair investigation because there was no collusion of any kind".
Mr Trump had been deferential toward Mr Mattis, saying on September 5 his defence chief would remain in his job.
"I think China meddled also".
When asked if other people would soon be leaving his administration, Trump responded, "Yeah, other people will go, sure".
"I think I'm very tough with him personally".
When asked about climate change, Trump backed off his claim that it is a hoax but said he doesn't know if it's man-made. He agreed with comments made by his wife Melania in a ABC interview last week, that there are some people in the White House who weren't trustworthy, saying: "I'm not a baby".More news: Student events to increase breast cancer awareness
Asked about Russian meddling in the 2016 election, Trump said China was interfering as well. I really mean it.
As Defense Secretary, Mattis has avoided the expressions of loyalty to Trump sometimes voiced by other Cabinet members.
"I'm going to change the subject again", Stahl moved on.
Later, Stahl, who has interviewed Trump three times, said this time, he was "so much more confident while giving the answers. I know these things", he said.
Stahl, "I disagree but I don't want to have that fight with you".
He added: "Of course I don't think about leaving, I love it here".
Stahl brought up Trump's now infamous speech at a political rally in MS in which he mimicked Christine Blasey Ford, the woman who testified before the Senate judiciary committee that Brett Kavanaugh attempted to rape her when they were both teenagers. "So I was very disappointed", he said.