Jerusalem (AFP) - Israeli Prime Minister Benjamin Netanyahu and his main opponent Benny Gantz sought to galvanise supporters Monday on the eve of a tense election with the political fate of the country's longest-serving premier in the balance.

The vote on Tuesday will be Israel's second in five months after Netanyahu suffered one of the biggest defeats of his political career when he failed to form a coalition after April polls.

Opinion polls indicate another tight race that may see ex-defence minister Avigdor Lieberman, Netanyahu's former right-hand man who is now a rival, play a kingmaker role with his campaign to "make Israel normal again".

The slogan is a reference to what the staunch secularist says is the heavy influence on politics of Israel's ultra-Orthodox Jewish parties.

Netanyahu has spent the past week seeking to boost turnout among his base, using a combination of warnings he could lose if supporters fail to go to the ballots and a flurry of announcements welcomed by right-wing nationalists, key to his re-election campaign.

On Sunday night, he went as far as to cancel his appearance at the final rally for his right-wing Likud party, saying he was instead holding an "emergency consultation", warning the potential of a low turnout could lead to his defeat.

For Israelis, it was a familiar tactic that Netanyahu has used repeatedly in the past -- though this time the risk may be greater since voter fatigue could play a role due to the repeat election.

Late Monday, Netanyahu showed no sign of slowing his efforts, posting a video on Facebook of himself at the Western Wall in Jerusalem's Old City, the holiest place Israel permits Jews to pray.

"I'm here to pray for the people of Israel, for the state of Israel," he said.

He has also hit on his other campaign themes: portraying himself as Israel's essential leader, dismissing his main opponents as "weak" and "left" despite their security credentials, and highlighting Israel's economic growth.

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- 'Historic change' -

Netanyahu has issued a controversial pledge to annex the Jordan Valley in the West Bank if he wins -- a third of the occupied Palestinian territory.

He says he would then move to impose Israeli sovereignty over settlements in the wider West Bank in coordination with US President Donald Trump, whose long-awaited peace plan is expected to be released after the vote.

"We find ourselves at the high point of an historic change in the history of the Jewish people and the state of Israel," Netanyahu wrote in Maariv newspaper, which gave space to both of the main candidates to spell out their positions.

His cabinet met ceremoniously in the Jordan Valley on Sunday, while the Palestinian Authority cabinet did the same in response on Monday.

"I think Israel after this decision has ended all the agreements signed with us," Palestinian prime minister Mohammed Shtayyeh said.

Gantz, an ex-military chief, has campaigned by presenting himself as an honourable alternative to Netanyahu, who is facing a possible corruption indictment in the weeks ahead.

He has repeatedly spoken of Netanyahu's willingness to form a coalition with far-right parties that could help him seek immunity from prosecution in parliament.

Gantz says he and his centrist Blue and White alliance want a unity government that the vast majority of Israelis would support.

"Blue and White under my leadership will change the direction of the ship of state of Israeli democracy," he wrote in Maariv.

"No more instigating rifts in an attempt to divide and conquer, but rather quick action to form a unity government."

Netanyahu has also faced criticism over the final days of the campaign due to his unfounded warnings the election could be stolen by fraud in Arab areas.

- Rivlin's role -

President Reuven Rivlin's choice to form the next government may depend on Lieberman, who polls show has gained popularity due to his campaign against ultra-Orthodox parties, an important part of Netanyahu's coalition plans.

He accuses them of seeking to impose Jewish religious law on Israel's secular population and wants legislation ending the exemption of ultra-Orthodox Jews from mandatory military service.

Opinion polls have given Likud and Blue and White around 32 seats each out of 120 in parliament, and around 10 for Lieberman's nationalist Yisrael Beitenu.

Lieberman prevented Netanyahu from forming a coalition after April polls when he refused to relent on his demand related to military service for the ultra-Orthodox.

It is not clear he will endorse Netanyahu as prime minister again, which could be enough for Rivlin to allow Gantz to try to form a government.

Both Netanyahu and Gantz will have to convince undecided voters before polls close.

"In the previous elections, I voted for Bibi because I believed in him, I trusted him and I saw he was doing a lot of good things," said Shimon Olitsky, a 25-year-old Jerusalem resident, using Netanyahu's nickname.

"But after what happened in the last elections, Bibi and the Likud have disappointed me on a personal level, and I'm looking for another alternative nowadays and I'm deliberating."