Donald Trump will not be adding the White House to his luxury resort holdings. The Donald on Monday took himself off the 2012 Republican presidential candidate list.

The wealthy real estate magnate with the complicated hairdo was the ultimate tease. He used his star power as a television celebrity to publicly flirt with a campaign, even though it was never entirely clear whether he really is a Republican.

Trump, who announced his decision in a written statement on Monday, was the loudest of many voices to call into question whether President Barack Obama was really born in the United States, becoming the unofficial leader of the ‘birther’ movement.

So the host of NBC-TV's ‘Celebrity Apprentice’ suffered a major blow when Obama produced a longer version of his birth certificate that was further proof of what most Americans had already decided that the president was born in Hawaii in 1961.

When Obama hammered home the point with some well-timed jabs at the April 30 White House Correspondents Association annual dinner, Trump was forced to endure humiliating laughter while sitting in the audience as a dinner guest.

"No one is prouder to put this birth certificate matter to rest than the Donald. And that's because he can finally get back to focusing on the issues that matter like, did we fake the moon landing?" Obama said at the time.

But Trump said in his announcement that he believes he would have won if he had decided to run.

"This decision does not come easily or without regret, especially when my potential candidacy continues to be validated by ranking at the top of the Republican contenders in polls across the country," he said.

Trump's support for the Republican nomination fell from 26 per cent in April to just 8 per cent in early May in surveys done by Public Policy Polling.

No Financial disclosures

By staying out of the race, Trump does not have to make public his financial holdings, which he would have been required to do if he had declared his candidacy.

He said his decision followed ‘considerable deliberation and reflection’ after weeks of an unofficial campaign.

"I maintain the strong conviction that if I were to run, I would be able to win the primary and ultimately, the general election," Trump said in a statement, adding that he is ‘not ready to leave the private sector.’

Trump had included himself among a number of prominent Republicans who had declared or were mulling a run for their party's nomination to oppose Obama, a Democrat who is seeking a second term.

Other leading hopefuls include former Massachusetts governor Mitt Romney and Newt Gingrich, who was speaker of the House of Representatives in the 1990s.

Speaking in New Hampshire last week, Trump expressed surprise at the public pummeling he has received since launching his potential candidacy.

Trump also suggested he will stay involved in Republican efforts to unseat Obama in 2012.

"I look forward to supporting the candidate who is the most qualified to help us tackle our country's most important issues ... and be the agent of change that this country so desperately needs," Trump said in his statement.

"I will continue to voice my opinions loudly and help to shape our politician's thoughts."