"There is no path for me to be the next president absent things that we don't want to see happen in this country," he told supporters in Iowa on Monday.

He added that he had spoken to Mr Trump and planned to campaign for him.

His departure further narrows down the field dominated by the ex-president.

On Monday night, Donald Trump finished with an overwhelming lead in Iowa, followed by Florida Governor Ron DeSantis in second and former UN Ambassador Nikki Haley in third.

Mr Ramaswamy, who finished in the fourth place, was the only candidate of the night to announce his departure from the race after Iowa held its first-in-the-nation vote.

He pledged to put "an America first candidate in the White House" and said that he planned to appear at a Trump campaign rally in New Hampshire in the coming days.

"Now, going forward, he will have my full endorsement for the presidency. And I think we're going to do the right thing for this country," he said.