Story highlights The comment underscores the volatility in Trump's relationship with Tillerson

Though the uneasy relationship continues, it is unlikely -- for now -- that Tillerson will leave

Washington (CNN) President Donald Trump, scorned by reports that Rex Tillerson called him a "moron" earlier this year, told Forbes in an interview released Tuesday that he has a higher IQ than his secretary of state.

The comment underscores the volatility between the two men after multiple reports that their relationship has frayed over the secretary of state's comment. Trump and Tillerson, along with Secretary of Defense James Mattis, will have lunch together at the White House on Tuesday afternoon.

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

Tuesday afternoon, White House press secretary Sarah Sanders said Trump's comment was simply a joke.

"The President certainly never implied that the secretary of state was not incredibly intelligent," she said. "He made a joke. Nothing more than that."

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