Donald Trump has seemingly challenged his secretary of state, Rex Tillerson, to an IQ test. This is just the latest chapter in their nascent feud after it was reported that the top US diplomat called the president a "f*****g moron".

In an interview with Forbes, Trump hit back at the claims that Tillerson may have used the foul language against him saying: "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."

Last week, NBC revealed that the secretary of state used expletive language to describe the president and was considering his position.

In a last-minute press conference, Tillerson denied that he ever considered quitting his post, but when asked about the "moron" comments, he simply described the question as "petty".

Speaking on Saturday 7 October, amid growing tensions between the state department and the White House, Trump said: "We have a very good relationship. We disagree on a couple of things. Sometimes I'd like him to be a little bit tougher. But other than that, we have a very good relationship."

Trump will be meeting with Tillerson and Defence Secretary Jim Mattis today (10 October) for talks about the ongoing political situation.

In the Forbes interview he also said that he was having "fun" in his new job. "I am having fun. I'm enjoying it. We're accomplishing a lot."

It isn't the first time that Trump's IQ has been centre stage, in 2013, he tweeted that people shouldn't feel insecure about his brain power saying: "Sorry losers and haters, but my I.Q. is one of the highest -and you all know it! Please don't feel so stupid or insecure,it's not your fault."

Tillerson and Trump
U.S. President Donald Trump talks with Secretary of State Rex Tillerson during a meeting with members of his Cabinet at the White House in Washington, U.S., June 12, 2017. REUTERS/Kevin Lamarque