In what is seen as a major surprise, partial results from the Iowa presidential caucus have Pete Buttigieg ahead of Bernie Sanders, Elizabeth Warren and Joe Biden.

Counting at the Democratic party caucus has been beset by technical difficulties but, with about 62 per cent of precincts reported, Mayor Pete Buttigieg and Senator Bernie Sanders have taken a lead in the Iowa caucus results.

Mr Buttigieg led with 26.9 per cent of the delegates, just ahead of Mr Sanders with 25.1 per cent of delegates. Senator Elizabeth Warren was third, with 18.3 per cent, followed by former vice president Joe Biden in fourth, with 15.6 per cent.

Senator Amy Klobuchar was in fifth, with 12.6 per cent.

More results were expected to be posted later on, as the Iowa Democratic Party continued to sort out a major technical malfunction that caused a delay in the totals.

Troy Price, the chair of the state party, said the delay was due to a “coding error” on the app used to report caucus results, which was discovered after irregularities began to appear during the tabulation on Monday night.

“The bottom line is that we hit a stumbling block on the back end of the reporting of the data,” Mr Price said.

He sought to assure the public that the results were accurate, saying the underlying raw vote was secure.

NEW: “The underlying data, the raw data, is secure. It was always secure.”

Iowa Democratic Party Chair Tony Price says data from last night’s caucuses is secure following technical issues that led to delay of results: https://t.co/rsw6xM2kAy pic.twitter.com/D7yu9xopQ0

— ABC News (@ABC) February 4, 2020

Speaking to reporters on an plane bound for New Hampshire on Tuesday morning, Mr Sanders said he was disappointed by the delay.

“Can’t understand why that happens but it has happened,” Mr Sanders said.

The Sanders campaign released its own internal results late Monday night, which showed Sanders in the lead. Mr Sanders also criticised Mr Buttigieg, who claimed victory on Monday night before any results were released.

“I don’t know how anybody declares victory without an official statement of election results, so we’re not declaring victory,” Mr Sanders said.

Mr Buttigieg did a series of TV interviews Tuesday morning in which he defended the decision, saying the campaign had far outpaced expectations, picking up support from all corners of the state.

“We are thrilled and absolutely consider that a victory,” he said on CBS This Morning. “Looking at all of the data that we’ve got, it was an extraordinary night.”

The pundits didn’t see our coalition coming.

This president won’t see it coming either. pic.twitter.com/LeBcaa7w3Q

— Pete Buttigieg (@PeteButtigieg) February 4, 2020

Ms Warren told supporters on Tuesday in Keene, New Hampshire, that the primary got off to a “bumpy start,” but that she was feeling good about the results.

“It’s a tight three-way race at the top,” she said. “We know the three of us will be dividing up most of the delegates coming out of Iowa.”

Mr Biden, meanwhile, sounded a bit downcast during a rally in the same state.

“As my mother would say, ‘Hope springs eternal,'” he said. “We’re not giving up, right? Not giving up.”

The Biden campaign sent a letter to the Iowa Democratic Party asking for a chance to respond before any caucus results were released.

At the rally, Mr Biden said the state party should take its time to get the results right.

“Now it’s time for New Hampshire to speak, and speak loudly,” he said.

-with AAP