Israeli Prime Minister Benjamin Netanyahu was on Monday given a 14-day extension to form a new government as he struggles to build a coalition after four weeks of intensive talks.

Such a move is far from unusual in Israel where it is almost unheard of for a single party to win an outright majority, and lengthy negotiations with multiple potential coalition partners are the norm.

Following last month's general election in which Netanyahu's rightwing Likud party won the largest number of seats, the Israeli premier was on March 25 tasked by Rivlin with forming a new government.

He was given 28 days to complete the task, but with the Wednesday deadline looming, and no agreement in sight, he went to Rivlin early on Monday to request the extension.

"I am giving you another 14 days to put together a government," Rivlin told Netanyahu in remarks broadcast on Israel's main radio stations.

"The people of Israel desperately needs a government because a transitional government has not got the confidence of the parliament," he told Netanyahu, wishing him success.

Netanyahu told Rivlin he needed the extension to build a stable government.

"We have moved forward and we are on the way but I need additional time so that it will be a stable government and so we can reach agreements on issues that are important to us in order to deal with all the challenges facing Israel," he said.

Netanyahu now has until May 6 to decide on the lineup of his next government, with his preference for a coalition with Likud's natural allies, the rightwing and religious parties.

Whatever the shape of the next coalition government, it will have to hit the ground running in order to shore up shattered ties with the administration of US President Barack Obama and address divisions at home.

It will also have to handle an emerging nuclear deal with Iran, vehemently opposed by Netanyahu, as well as the imminent threat of Palestinian legal action at the International Criminal Court.

- No unity govt deal -

The vice chairman of the Movement for Quality Government in Israel, Michael Partem, said that most prime ministers had needed the two-week extension to put together a majority coalition.

"In most instances there is an extension, it's certainly very common," Partem told AFP. "It's irksome but it's not a major flaw in the system."

Despite nearly four weeks of intensive negotiations, Netanyahu has not yet managed to reach agreement on the rightwing-religious government he was hoping to form with a majority of 67 in the 120-seat parliament.

That would consist of his Likud (30 seats), the far-right Jewish Home (eight), the hardline anti-Arab Yisrael Beitenu (six), the ultra-Orthodox parties Shas (seven) and United Torah Judaism (six) and the centre-right Kulanu (10).

As the talks dragged on, rumours surfaced last week that Netanyahu had turned to the centre-left Zionist Union, which won 24 seats, with a view to forming a national unity government.

But Zionist Union leader Isaac Herzog has firmly scotched rumours of a deal, reiterating his party's insistence on going into opposition.

"I said after the election results came in that we were headed to the opposition. That’s not by default. That is our preference," he said late Saturday.

If Netanyahu is unable to form a coalition in the next fortnight, Rivlin must assign another party leader to the task, again with a 28-day deadline.

If that fails, he must select a third person who has just 14 days to complete the task. Should that end in failure, Rivlin would call a new election.