The mainly Arab Joint List alliance made the announcement at roughly the same time as its leader, Ayman Odeh, published an opinion piece on the New York Times website speaking of the move.

It was the first time since 1992 that majority Arab parties have endorsed a candidate for prime minister.

Shortly later, Odeh told Israeli President Reuven Rivlin the alliance's priority was to oust Prime Minister Benjamin Netanyahu from power, and was therefore recommending Gantz.

He made the comments as Rivlin consulted with Israeli political parties on who should form the next government following Tuesday's deadlocked general elections.

The Joint List won 13 seats in the election, making them the third-largest force in the 120-seat legislature.

One party within the alliance, accounting for three seats, signalled it was against the decision.

Even with the endorsement of all 13 seats, Gantz and his centrist Blue and White alliance would fall short of 61 needed for a majority. 

He is expected to have the endorsement of 57 seats during Rivlin's consultations. Netanyahu is expected to receive 55.

Rivlin has said he believes a unity government should include both Netanyahu's Likud and Blue and White in order to create a stable coalition.