Former Arkansas governor Mike Huckabee says he has been "named to head up" what would be an unconstitutional 2024 re-election campaign for Donald Trump.

Mr Huckabee, father of former White House press secretary Sarah Sanders, made the explosive claim in a pair of tweets on Thursday afternoon in which he also said the US president was "eligible" for a third term due to congressional investigations into him.

"Greatly honored to be asked to chair @realDonaldTrump re-election campaign for @POTUS in 2024. Gives me lots of time to plan!" Mr Huckabee said without providing evidence.

He added: "I'll be on @seanhannity 2nite @FoxNews at 9pm ET and will explain how @realDonaldTrump will be eligible for a 3rd term due to the illegal attempts by Comey, Dems, and media, et al attempting to oust him as @POTUS so that's why I was named to head up the 2024 re-election."

It was unclear if Mr Huckabee was serious, but there is no indication there exists any official 2024 re-election campaign for Mr Trump, who faces a battle just to win a second term in November 2020.

The US constitution expressly forbids presidents from serving more than two terms in the White House.

Mr Trump has repeatedly joked about serving three or more terms in remarks to reporters and at election rallies, but normally insists he is only doing so to provoke liberals.

Some commentators have suggested he repeatedly muses about doing so as a means of normalising the concept before making a serious attempt.

Mr Trump hinted at doing so in August when he suggested the FBI has "stolen time" from him due to the bureau's probe into links between the Trump campaign and Russia.

"The disastrous IG Report on James Comey shows, in the strongest of terms, how unfairly I, and tens of millions of great people who support me, were treated," he tweeted at the time, in reference to a Justice Department report critical of the former FBI director.

"Our rights and liberties were illegally stripped away by this dishonest fool. We should be given our stolen time back?"