Israel's president Isaac Herzog says he will name a candidate to form the next government by Sunday, after a majority of lawmakers endorsed opposition leader Gadi Eisenkot over Prime Minister Benjamin Netanyahu.

Herzog spoke on Thursday after marathon consultations with parties elected to the 120 seat Knesset. Some 67 lawmakers recommended Eisenkot, a former military chief, while 46 backed Netanyahu. In televised remarks he cautioned that although the consultation numbers look clear, mutual vetoes between and within blocs make it hard to say who has the best chance of assembling a stable coalition. He plans further personal talks with party leaders over the Israeli weekend and a decision on Sunday.

October's election left neither camp with an obvious majority. Netanyahu's Likud took the most seats of any single party with 27, yet his wider religious nationalist coalition finished on 53. Eisenkot's alliance of four Jewish led parties spanning centre left to right won 48. Two parties representing Israel's Palestinian minority together took a record 19 seats.

Eisenkot, like Netanyahu, has ruled out a formal government with the Arab led parties. Both of those parties nonetheless recommended him, giving him the endorsement of a comfortable majority of lawmakers. His Yashar party said 67 recommendations were the most any candidate had received since 2015 and urged Herzog to hand him the mandate quickly so he could build a national emergency government.

Netanyahu suffered a further setback when United Torah Judaism, a longtime ultra Orthodox ally, declined to recommend anyone, breaking with him over the failure to pass legislation exempting ultra Orthodox men from military service. Allies of Eisenkot argue that party's support could still be won with the right offer, leaving Netanyahu with little realistic path to a majority.

Once nominated, a candidate has 28 days to form a government, with a possible 14 day extension. Netanyahu remains caretaker prime minister until a coalition is sworn in or fresh elections are called if every attempt fails. He has seized on an election officials' inquiry into possible vote tampering to cast doubt on the result, accusing Arab led parties of stealing the vote, claims critics say are meant to undermine a defeat he denies.