President Trump still has confidence in Secretary of State Rex Tillerson, he said Tuesday.

The president reaffirmed his support for Tillerson before a meeting in the Oval Office with former Secretary of State Henry Kissinger.

When asked if he has confidence in Tillerson, Trump said, "Yes."

He also denied undercutting Tillerson.

"No, I didn't undercut anybody. I don't believe in undercutting people," he said.

Trump was accused of going against Tillerson by telling him to stop negotiating with North Korea in a tweet earlier this month. The tweet came after revelations Tillerson had a method of directly communicating with the North Koreans.

Trump and Tillerson have reportedly gone head to head in recent months. NBC News reported last week Tillerson threatened to resign in July and called Trump a "moron" after a meeting at the Pentagon.

But the secretary of state gave an impromptu press conference last week dismissing rumors he would step down from his post, and dodged a question about whether he did, indeed, call Trump a "moron."

In an interview with Forbes published Tuesday, Trump said if it's true Tillerson called him a "moron," they should compare IQ tests to determine which man is smarter.

"I think it's fake news, but if he did that, I guess we'll have to compare IQ tests," the president said. "And I can tell you who is going to win."