(Adds Iowa events, changes dateline, previous WASHINGTON)

By Jeremy Pelofsky

JOHNSTON, Iowa, Dec 21 (Reuters) - The Iraq war dominated the U.S. presidential campaign on Friday, with Democrat Hillary Clinton facing charges she flip-flopped on withdrawing forces and the White House rebuffing Republican Mike Huckabee's criticism of its foreign policy.

As the violence in Iraq has fallen in recent months in response to the deployment of additional U.S. troops, the war has become less of a daily issue among candidates for the November 2008 election.

But less than two weeks before Iowa kicks off the state-by-state party nomination contests, Democrats seized on the former first lady's suggestion on Wednesday that U.S. troops could come home within a year. Previously she had declined to commit to withdrawing all troops within 5 years.

"Many times she's said something that's different than what she's just said," former North Carolina Sen. John Edwards, the told reporters. "I was very surprised by it, particularly since we've been in a campaign for a year now."

Clinton's campaign argued she has not changed her position, but rather has consistently supported withdrawing one to two combat brigades from Iraq each month. There are 20 brigades in Iraq now with 3,000 to 5,000 troops each.

"I think we can bring nearly everybody home, you know, certainly within a year if we keep at it and do it very steadily," said Clinton, who would be the country's first female president if elected.

Edwards favors withdrawing U.S. troops within nine to 10 months while retaining a military presence in nearby countries. But defense officials have said bringing more than one brigade home a month would be challenging.

On the Republican side, Secretary of State Condoleezza Rice in Washington said a critique of the administration's foreign policy by Huckabee last week was "ludicrous."

The former Arkansas governor and Baptist minister said the administration's "arrogant bunker mentality" had been counterproductive.

"LUDICROUS IDEA"

"The idea that somehow this is a go-it-alone policy is just simply ludicrous," Rice said in an unusual intervention in the internal Republican battle.

Huckabee's campaign was not immediately available for comment.

Other leading Republican candidates have refrained from criticizing President George W. Bush despite his low approval ratings, and Bush has declined to pick a favorite in the race to succeed him.

Arizona Sen. John McCain has been gaining momentum in New Hampshire, according to a second poll in two days. A USA Today/Gallup poll showed Mitt Romney, former governor of neighboring Massachusetts, leading McCain 34 percent to 27 percent. Previously Romney had held a double-digit lead.

Clinton, a U.S. senator for New York, led the Democratic field for much of the year but her poll advantage in early nominating states of Iowa and New Hampshire has disappeared. A USA Today/Gallup poll of New Hampshire voters found Clinton and Illinois Sen. Barack Obama tied on 32 percent with Edwards behind at 18 percent.

New Mexico Gov. Bill Richardson, a former U.S. ambassador to the United Nations who lags the top three in the race, also criticized Clinton over her Iraq comment. "Has anything changed about the logistics, besides her position in the polls?" he said in a statement.

While Clinton campaigned in New Hampshire, her husband, former President Bill Clinton, went to Iowa to argue that his wife had the most experience to face world challenges.

"If she's elected, we will have immediately a president who is credible on national security and military affairs, committed to diplomacy and cooperation, widely respected around the world," he said told voters in Columbus Junction, Iowa.

As other candidates campaigned in New Hampshire and Iowa ahead of the Christmas holiday, Republican Rudy Giuliani took a day off at home in New York after being hospitalized for flu-like symptoms. (Additional reporting by Andy Sullivan in Washington, editing by Alan Elsner.) (To read more about the U.S. political campaign, visit Reuters "Tales from the Trail: 2008" online at http://blogs.reuters.com/category/trail08/)

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