Donald Trump on Wednesday announced he is endorsing Mitt Romney for the Republican presidential nomination, after initial reports said he would throw his support behind Newt Gingrich.

The businessman told reporters he decided to support Romney after getting to know him better in recent months.

"It's my honor, real honor to endorse Mitt Romney. Mitt is tough, he's smart, he's sharp. He's not going to allow bad things to continue to happen to this country. Governor Romney, go out and get ‘em," said Trump.

Trump also said he will not run for president as an Independent if Romney becomes the nominee.

Meantime, Newt Gingrich is latching onto Romney's comment on Wednesday about caring about the poor.

Gingrich says "we should care about the very poor", while Romney says he was focused on the middle class, with safety nets in place for the very poor.

Both candidates are campaigning in Nevada ahead of Saturday's caucuses.