Israel's ex-military chief Benny Gantz, Prime Minister Benjamin Netanyahu's main rival, was the only candidate nominated Thursday for speaker of parliament, a move that could lead to an emergency alliance between the two men.

Gantz and Netanyahu have gone head-to-head in three inconclusive elections over the past 12 months, with neither securing enough support to form a viable coalition.

Spurred on by the need to contain the COVID-19 pandemic, including more than 2,600 confirmed Israeli cases, there have been widespread calls for an emergency alliance between the rivals.

At a session in the Knesset, Israel's parliament, on Thursday, Gantz was named as the only candidate to succeed Netanyahu ally Yuli Edelstein, who resigned as speaker under pressure on Wednesday.

"I present Benny Gantz, the chairman of Blue and White - the leader of Blue and White - as a candidate for Knesset speaker," said Avi Nisenkorn, a lawmaker from Gantz's centrist alliance.

A formal vote to elect Gantz was underway early on Thursday evening.

Unity government? 

A staunch ally of Netanyahu's right-wing Likud party, the ultra-Orthodox United Torah Judaism party, has committed to backing Gantz as speaker.

Defence minister Naftali Bennett, a Netanyahu ally who leads the nationalist Yemina party, also applauded Gantz's move, welcoming him to a "unity government."

No unity government has been confirmed.

But a source within the Blue and White party, who requested anonymity, told AFP that Gantz's bid to become speaker was part of an effort to form an emergency government with Likud.

Likud in a statement said details emerging in the media about the composition of a unity government were just "rumours."

Gantz was charged with forming a government after the March 2 vote -- a task that had proved impossible following two previous elections last year, given the deep divisions within the anti-Netanyahu camp.

Those divisions quickly appeared to deepen after Gantz put himself forward as speaker on Thursday.

Two key partners in the Blue and White alliance -- the Telem and Yesh Atid parties -- immediately filed paperwork to split from Blue and White, spokesmen for both factions said.

Telem's Moshe Yaalon and Yesh Atid head Yair Lapid were widely thought to have opposed a unity deal with Netanyahu.

Netanyahu has made a series of offers to Gantz on a unity government, including deals that would see the premier's job rotate between the two men.

"There's deep unrest among all parts of the nation, we must put it aside," the premier said in a televised address late Wednesday focusing on anti-coronavirus measures.

"I call for the immediate formation of a national unity government to deal with the crisis."