The billionaire businessman said it is only the former Massachusetts governor who can defeat incumbent Barack Obama in the November presidential elections, www.firstpost.com reports.

"You look at what's going on with China, you look at what's going on with the other OPEC nations and how they are absolutely destroying this country, and you are the only one who talks about it," Trump told reporters in Las Vegas.

"So that was very important to me. I thought he did very well in the debates; that was very important... I think if he debates that well, I don't think Obama will fare well against him," Trump said while endorsing Romney standing next to him.

"Mitt is tough, he's smart, he's sharp, he's not going to allow bad things to continue to happen to this country that we all love ... So Governor Romney, go out and get them, you can do it," the reality TV star said making the announcement.

Trump's endorsement of Romney came after a day of speculation in which news reports said he would endorse Newt Gingrich, former Speaker of House of Representatives.

However, media outlets were not sure how much this endorsement would help Romney, who is currently front runner among the four Republican presidential candidates

A Pew survey last month found that 64 per cent of definite and likely GOP voters said an endorsement from the reality television star would make no difference to them.

"Donald Trump's endorsement of me today sends a strong signal that he believes we have the best chance to make President Obama a one-term president," Romney said.

We share both a background in the private sector and a belief that Washington needs to get out of the way of small business, he said.

"His support is a sign that business leaders are fed up with Washington and want someone with actual experience creating jobs and working in the real economy in the White House," Romney said.

The White House tried to make a light of the Trump's endorsement. "You know, I'm not going to comb over that question," the White House Press Secretary, Jay Carney, told reporters at his daily news conference when asked about it.

Republican presidential candidate, Ron Paul, questioned the decision of Trump. "Please explain to Republican voters in Nevada why they should consider the opinion of a billionaire from New York who endorsed the arch enemy of all Republicans in Nevada, and really the enemy of all Republicans in the US," Paul asked.