Donald Trump proposed an “IQ tests” face-off with Secretary of State after Rex Tillerson allegedly called the president a “moron” and disparaged his grasp on foreign policy.

In an interview with Forbes magazine published Tuesday, the president fired a shot at the nation’s top diplomat over the “moron” revelation, first reported by NBC News and confirmed by several other news organizations, including The Washington Post.

“I think it’s fake news,” Trump said, “but if he did that, I guess we’ll have to compare IQ tests. And I can tell you who is going to win.” Trump’s dare is the latest evidence of what White House officials have described as a breach of trust between the president and secretary of state.