Jewish presidential candidate Bernie Sanders has narrowly lost the Iowa caucuses to Democratic Party frontrunner Hillary Clinton.

If Vermont Senator Sanders had won the caucuses, he would have become the first Jew - and the first non-Christian - to win a US presidential primary.

But on Tuesday morning, with one precinct left to report in the first primary ahead of the national election in November, Sen. Sanders had 49.6 per cent of the vote, with Mrs Clinton ahead on 49.9%.

The margin of victory was the smallest in the state’s history of Democratic caucuses.

Sen. Sanders told supporters in the state that the primary was “a virtual tie,” adding that “what Iowa has begun tonight is a political revolution.”

The result was a blow for the self-proclaimed “democratic socialist,” as Iowa had represented one of his best chances for winning a state.

But he will have the chance to regain some momentum by winning the New Hampshire primary on February 9, where he currently leads Mrs Clinton in the polls.

The third Democratic presidential candidate, Martin O’Malley, suspended his campaign after winning 0.5 per cent of the Iowan vote.

In the Republican caucuses, Texas Senator Ted Cruz defeated billionaire businessman Donald Trump with 27.7 per cent of the vote, compared to Mr Trump’s 24.3 per cent.