WASHINGTON – The White House dismissed Donald Trump as a "sideshow" on Sunday and said there was no way the billionaire businessman would be "hired" by the American people as president in 2012.

Trump, renowned for his New York bluster, is considering a tilt at the White House and according to some polls is running second among prospective Republican candidates, behind former Massachusetts governor Mitt Romney.

As part of his flirtation with a presidential bid, Trump has controversially brought up the non-issue of Obama's birthplace.

The president was born in the US state of Hawaii and released a certificate of live birth to prove it in June 2008, but some on the right-hand fringes of American politics still like to pretend it is an issue.

"I think I saw Donald Trump kind of rising in some polls and given his behavior with respect to the last couple of weeks I hope he keeps on rising," Obama's campaign adviser David Plouffe told ABC's "This Week" program.

"I think there's zero chance that Donald Trump would ever be hired by the American people to do this job."

Despite strong criticism, Trump refuses to be bowed on the "birther" issue -- presidents must be born in the United States -- and says he has sent investigators to Hawaii to research the matter.

"There may be a small part of the country that believes these things, but mainstream Americans think it's a sideshow," said Plouffe.

Many observers remain unconvinced that Trump, a 64-year-old rebranded Republican who has switched party affiliation a few times over the years, is serious about running and some believe he is simply courting media attention.