Former Indiana mayor Pete Buttigieg is leading the Iowa caucus with 62 per cent of the precincts reporting, with former vice president Joe Biden falling back into fourth spot in the US Democratic primary race.
Mr Buttigieg received 26.9 per cent of the vote with Bernie Sanders close behind on 25.1 per cent, according to partial results from the first vote to pick a Democratic White House candidate.
Elizabeth Warren was third on 18.3 per cent and Joe Biden fourth on 15.6 per cent.
The day was marred by a long delay due to what Iowa's Democratic Party called "inconsistencies in the reporting of three sets of results".
A coding error in the app used by the party has been blamed for the delays.
Image: AP
