By Sam Youngman

WASHINGTON (Reuters) - Republican presidential candidate Mitt Romney said on Tuesday that he will not attend a controversial December 27 debate to be moderated by real estate magnate Donald Trump, as have candidates Ron Paul and former Utah Governor Jon Huntsman.

Romney told Fox News' Neil Cavuto that he will not participate in the Iowa debate, which has drawn fire from Washington Republicans as well as two of Romney's competitors.

He gave no reason, but other Republicans have expressed concern that the event could be an embarrassment with Trump in control.

Trump flirted with a run for the Republican 2012 presidential nomination earlier this year and was derided for pushing a discredited charge that Democratic President Barack Obama might not have been born in the United States.

Romney said on the show that he had spoken with Trump and informed the multimillionaire businessman and entertainer that he will not attend.

The only candidates so far to agree to the debate are rising Republican Newt Gingrich and former Senator Rick Santorum.

A campaign spokesman for Texas Representative Paul said that Trump moderating a debate would result in "an unwanted circus-like atmosphere."

"The selection of a reality television personality to host a presidential debate that voters nationwide will be watching is beneath the office of the presidency and flies in the face of that office's history and dignity," campaign spokesman Jesse Benton said.

In the days following Trump's announcement of the debate, which will be co-hosted by Newsmax, Republican strategists in Washington worried aloud that by participating in the debate, the Republican candidates would appear foolish or out-of-touch with voters.

Ari Fleischer, former press secretary for Republican President George W. Bush, said on Twitter that Trump's idea to moderate a debate is "absurd."

"I hope all GOP candidates turn him down."

And veteran Republican strategist Karl Rove has urged the Republican National Committee to call on Trump to cancel the event.

(Editing by Jackie Frank)