Most of the top Republican and Democrat candidates have been crisscrossing Iowa for days, pushing their message home.

The caucuses - simultaneous meetings held at 1,784 locations across the state - will be held on 3 January.

Thousands of political activists have been dispatched by both parties to attend political meetings in the state.

On the Democratic front, a Reuters/C-Span/Zogby poll released at the weekend gives Hillary Clinton a slight lead in Iowa, with Barak Obama and John Edwards fighting for second place.

Mrs Clinton was scheduled to spend New Year's Eve at a late-night rally with her husband Bill in Iowa's capital Des Moines.

Mr Obama was to cross the state attending a total of five rallies on Monday.

Momentum

Mr Edwards, who polls show has gained momentum in Iowa, was sending out hundreds of volunteers on a state-wide canvass.

The same Reuters/C-Span/Zogby poll also suggested a tight Republican contest between former Arkansas Governor Mike Huckabee and former Massachusetts Governor Mitt Romney.

"It's about as close as you can get at the top in both races," pollster John Zogby said. "But it's still very uncertain."

Republican John McCain solidified his hold on third place, with former New York Mayor Rudy Giuliani, who has maintained a low-key presence in Iowa, some way behind.

A McClatchy-MSNBC poll, also released over the weekend, gave Mr Edwards a single percentage point lead in Iowa over Mrs Clinton, while Mr Romney was just ahead of Mr Huckabee.

On Sunday, Mrs Clinton said that even third place in Iowa would not spell disaster heading into the New Hampshire primary on 8 January.

"I believe that this campaign will be bunched up, I think the history out of Iowa shows that a lot of people live to fight another day," Mrs Clinton told ABC News.

Other leading candidates took to the airwaves on Sunday, with Mr Huckabee using the opportunity to lash out at his nearest rival.

He accused Mr Romney of trying to mislead voters with adverts targeting his record on taxes, illegal immigration and foreign policy views.

Experience

"Mitt Romney is running a very desperate and, frankly, a dishonest campaign," Mr Huckabee said on NBC. He also questioned whether Mr Romney could be trusted with the presidency.

For their part, Mr Romney's team accused Mr Huckabee of "testiness and irritability".

In his closing message on the NBC's Meet the Press on Sunday morning Mr Obama acknowledged that the criticism about his lack of experience in Washington might be taking a toll.

"That may have some effect, but ultimately I'm putting my faith in the people of Iowa and the people of America that they want something better," he said.

Mrs Clinton, on the other hand, played on her experience, telling This Week that she had once been "intimately involved in so much that went on in the White House, here at home and around the world".

Candidates who do well in Iowa and New Hampshire can gain momentum and media attention, establishing themselves as front-runners.

BBC News, December 31, 2007