Donald Trump endorsed Mitt Romney for president Thursday, saying he's impressed by the Republican candidate's debate prowess and believes he could easily beat President Obama in November.

"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," Trump said in Las Vegas, telling the candidate to "go out and get 'em."

The real estate mogul, speaking briefly with reporters before the announcement, said that even though he "never knew" Romney before the race began, he's come to know him in recent months.

"His general attitude and the last two debates were very impressive," Trump said.

He also cited Romney's position on China, calling the former Massachusetts governor "the one person who continually mentions China and OPEC."

The endorsement comes after Romney soundly defeated Newt Gingrich in the Florida Republican presidential primary on Tuesday, and ahead of Nevada's caucuses this Saturday. Polls show Romney with a significant lead in the upcoming contest.

Earlier reports had claimed Trump was planning on endorsing Gingrich at Thursday's event. But sources close to the Romney campaign confirmed to Fox News Thursday morning that the real estate mogul would back Romney.

Trump told Fox News that he likes Gingrich "very much," but that Romney "has really stepped up more than anybody else" on issues like China.

Romney said Thursday that the endorsement "means a great deal to me," citing Trump's job-creation record.

He also joked, "There are some things that you just can't imagine happening in your life -- this is one of them."

It's not clear whether the endorsement can yield a bump for Romney. A Fox News poll last month suggested the reality TV star and businessman could do a candidate more harm than good.

In the poll, 27 percent said his endorsement would make them less likely to support a candidate. Only 10 percent said Trump's support would make them more likely to vote for a candidate. For most people, the endorsement would make no difference.

The Democratic National Committee wasted no time Thursday producing a web video mocking the Romney-Trump alliance. The video suggested the reason Trump is backing Romney is, "They both like firing people" -- in reference to Trump's "Apprentice" catch phrase, and Romney's recent comment in which he said, in reference to under-performing health insurers, "I like being able to fire people who provide services to me."

Trump flirted with the idea of a Republican presidential run last year, before bowing out. But he also has declined to rule out the possibility of a third-party run.

However, Trump said Thursday that if Romney is the nominee, he will not make a third-party run for the presidency.

"Certainly if Mitt gets the nomination and he runs, I wouldn't be running again," he told Fox News. "If for some reason something happens, then it's open season."