US Democrats in first key battle

Candidates have been campaigning across the state for months

Democrats wanting to challenge George W Bush are facing their first major test, with a tight race in the state of Iowa.

Candidates are making final efforts to sway voters before what may be a record turnout for the local caucus gatherings which start at 1830 (0030 Tuesday GMT).

Results from the caucuses emerge within hours, with implications more important than the mere allocation of delegates who go on to pick the Democrat nominee.

As the first closely watched test, results may boost or bury candidates.

Opinion polls from the midwestern state, traditionally the first to make its choice for presidential nominee, show the race between Howard Dean, John Edwards, Richard Gephardt and John Kerry is too close to call.

A win for Mr Dean would add to his status as front-runner, while anything but a strong showing could spell doom for the Gephardt campaign.

Iowa voters' choices

In pictures

Mr Gephardt is a congressman for the neighbouring state of Missouri and has played up his own midwestern credentials.

Over the next few hours, the campaigns will be knocking on doors and working the telephones to ensure their supporters turn out.

The BBC's Rob Watson in the state capital, Des Moines, says it is expected that as many as 100,000 Iowans will brave below-freezing temperatures to express their preferences.

Neither Mr Kerry nor Mr Edwards had been expected to win in Iowa and a high placing would give their campaigns new impetus as the focus switches to areas where each should count on strong support, correspondents say.

The next vote comes later this month in New Hampshire - neighbour to Mr Kerry's home state of Massachusetts - and is followed by the primary in South Carolina, where North Carolina senator Mr Edwards was born.

Presidential pick

On Sunday, former US President Jimmy Carter gave a boost to Mr Dean's presidential candidacy on the eve of the first key contest in the 2004 race.

DEMOCRATIC CONTENDERS Howard Dean John Edwards Dick Gephardt John Kerry Dennis Kucinich Al Sharpton [Joe Lieberman and Wesley Clark are not competing in Iowa] Guide: Candidates and issues State profile: Iowa

He described the former Vermont governor as "a strong and open advocate of peace" and said the war had been "a sustained demonstration of tragedy".

Mr Dean, who began his political career as a supporter of Mr Carter in Vermont, thanked the former president for getting him involved in politics.

He praised the ex-president as "a moral example for all Americans" and said: "I hope to follow the example of Jimmy Carter."

Dead heat

Civic leaders in the state have predicted that the virtual dead-heat will boost voters' attendance.

WHAT IS A CAUCUS? Derives from an Indian word meaning meeting Instead of going to the polls and casting a vote, party members attend about 2,000 private meetings across Iowa, hold a debate and declare their preference Participants also elect delegates to communicate their choice to county party conventions, which themselves choose delegates to do the same at state and then national level Critics of the caucus system say it is too laborious Supporters of the system say it encourages grassroots participation Q&A: Iowa caucuses US election glossary

Caucuses are meetings held at venues throughout the state - from public halls to private houses - where grassroots party members elect delegates to the national party convention later this year.

Those delegates will determine the party's presidential and vice-presidential candidates.

Many other states use party elections called primaries - rather than caucuses - to test the candidates' popularity.

A new survey published on Sunday, conducted by pollster John Zogby for Reuters news agency, put Mr Kerry at 24.4%, with Mr Dean narrowly behind at 23.1%.

Mr Gephardt was on 18.8% and Mr Edwards at 18.4%. But with a margin of error of 4.5%, there was no clear leader among the four.

Another poll published on Sunday by the biggest newspaper in the state, the Des Moines Register, also had Mr Kerry in the lead, with 26%.

The paper put Mr Edwards second at 23%, followed by Mr Dean with 20% and Mr Gephardt at 18%.