Senator Barack Obama was leading the Democratic caucus in the western state of Wyoming on Saturday, in the latest contest in the state-by-state battle to represent the party in November presidential elections. ( dpa )
Obama was leading with 59 per cent of the vote to opponent Hillary Clinton's 40 per cent, with 78 per cent of the state's caucus sites reporting results, CNN said.
Nearly 60,00 party members had turned out for the party meetings in the generally Republican-leaning state, an unusually high turnout in the sparsely populated state of about 500,000.
Only a few hundred Democrats turned out for the party's caucus in 2004, but this year's long, close race between Clinton and Obama has generated interest in states that traditionally have had little say in determining the party's candidate.
The battle between Obama, 46, and Clinton,60, took an increasingly nasty tone in the run-up to caucuses in Wyoming on Saturday and primary voting on Tuesday in Mississippi.
Only a handful of delegates are up for grabs in both states. Clinton lags behind Obama in the delegate count needed to secure the nomination at the party's convention in Denver in August by less than 100 delegates out of the 2,205 needed.
She had 1,424 delegates compared to Obama's 1,520 heading into Saturday's contest, according to CNN.
Only centre-left Democrats caucused in Wyoming on Saturday, and the centre-right Republicans held their contest there in January. Republican Senator John McCain sealed his grip on the nomination on Tuesday with primaries in Ohio, Texas, Vermont and Rhode Island.
With the race so close, there is pressure for repeat voting in two states whose primary results were dismissed because of their early timing in January - Florida and Michigan.
Obama is expected to win the contests Saturday in Wyoming and Tuesday in Mississippi, after which the two candidates will have more than a month to prepare for the last big-state primary in delegate - rich Pennsylvania on April 22.
Under Democratic rules, delegates are assigned proportional to the vote, meaning a candidate can lose the majority vote but still get a sizeable number of delegates.