President Trump attacked Secretary of State Rex Tillerson in a new interview in which he suggests that he's smarter than the top member of his Cabinet.

Speaking to Forbes magazine, Mr. Trump was reacting to the report that Tillerson had previously called the president a "moron."

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

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Asked about Tillerson's IQ at a State Department press briefing later, spokeswoman Heather Nauert said simply, "It's high."

She described Tillerson as someone "who can put things together" due to his background as an engineer, and said he felt no need to justify how smart he is.

"The president is allowed to joke," Nauert said, and Tillerson is "more than fine with that."

The president was scheduled to have lunch with Tillerson and Defense Secretary James Mattis Tuesday afternoon after he met with former Secretary of State Henry Kissinger in the Oval Office.

This comes just days after Tillerson delivered abruptly scheduled remarks in which he pledged allegiance to Mr. Trump and shot down a report that said he was on the verge of resigning from his position over the summer.

"I have never considered leaving this post," Tillerson said last Wednesday at the State Department about what he called an "erroneously" reported story.

However, while Tillerson said that the detail from the report about him calling the president a "moron" was "petty," he didn't deny having called him that.