US Republicans Mitt Romney and Rick Santorum finished neck-and-neck in the first voting to select a Republican presidential candidate to take on President Barack Obama.

Returns showed the two candidates winning roughly 25 percent of the vote each. With 100 percent of precincts reporting, Romney squeaked ahead in the final count by a mere eight votes.

The former Massachusetts governor won 30,015 votes over 30,007 for Santorum, Iowa officials announced after the two men slugged it out to a nail-biting photo-finish.

Romney congratulated his opponents for weel-run cmpaigns and then trained his sights on Obama.

"This has been a failed presidency," he said, calling Obama "in over his head" and vowing to "get America back to work."

On Tuesday, the candidates had crisscrossed the state in their late bids for support in the first contest of the 2012 US presidential campaign.

At least three of the candidates - Romney, former senator Santorum and Texas congressman Ron Paul - appeared to have a shot at finishing top of the pile in Iowa.

Tight race was predicted

Surveys of likely caucus goers showed that frontrunner Romney, the favorite of the Republicans' business wing, was in a tight race with libertarian Paul and Santorum, who hopes to appeal to the state's Christian conservatives.

A poll carried out by the Des Moines Register newspaper in the run-up to the caucuses suggested that as many as 41 percent of Iowa Republicans were either undecided or could imagine changing their minds in the voting booth.

Texas Governor Rick Perry, former House Speaker Newt Gingrich and Minnesota congresswoman Michele Bachmann all trailed the top three in polls. Another candidate, Jon Huntsman, a former US ambassador to China, has decided not to visit Iowa.

Iowa's caucuses are better known more for weeding out candidates than picking the future president. In 2008, former Arkansas governor and Baptist preacher Mike Huckabee won the caucuses with 34 percent of the vote, only for John McCain to go on and seal the Republican nomination with relative ease.

Author: Richard Connor, Gregg Benzow (AP, Reuters)
Editor: Nigel Tandy