Retired pediatric neurosurgeon and former presidential candidate Ben Carson is planning to endorse Donald Trump during a Palm Beach, Florida press conference on Friday morning local time, a number of media reports have revealed.

According to the Washington Post, sources said the endorsement was finalised on Thursday when Carson met with Trump at the latter's club, the Mar-a-Lago.

The news comes as Carson told Fox News Radio that he was "certainly leaning" towards Trump instead of Ted Cruz, even though he has been slammed by the Republican front-runner several times in the past, including calling voters "stupid" to believe stories Carson had told about his life.

“There’s the Donald Trump that you see on television and who gets out in front of big audiences, and there’s the Donald Trump behind the scenes. They’re not the same person,” Carson said in his interview with John Gibson.

“One’s very much an entertainer, and one is actually a thinking individual.”

Carson had dropped out of the presidential nomination race just last week after failing to secure one primary content. He suspended his campaign after telling supporters that he saw “no path forward” with his bid.

However, it is said the conservative now believes Trump is the GOP's best bet of beating the democrat candidate and winning the next US presidential election.

"You have to consider all the information, who is most likely to win, and what kind of shenanigans will drive voters away so they will not participate in the process," Carson said in a Wednesday interview with CNN when asked whether he would throw his weight behind Trump or Cruz.

"We have to be very careful in all those things."

Carson's endorsement of Trump is expected to significantly boost the real estate magnate's campaign. It will also make Carson the second former GOP candidate to officially back Trump, after New Jersey Governor Chris Christie did the same last month.