(Reuters) - Israel is expected to hold early elections on September 4 after the ruling Likud party submitted a bill to dissolve parliament, with opinion polls on Thursday giving Prime Minister Benjamin Netanyahu a clear lead.

Although a national vote was not due until 2013, tensions within Netanyahu´s rightist coalition over domestic issues, such as military draft for ultra-orthodox Jews, have convinced the prime minister to push for a pre-emptive ballot.

Israeli officials have said electioneering would not affect their stance on Iran´s nuclear program, but many analysts believe the government would not carry out a long-threatened attack on the Islamic republic in the run-up to a vote.

Netanyahu is marking a week of mourning following the death of his father and is widely expected to agree on an election date when he returns to official duties on Sunday.

"There is agreement among most of the factions in the coalition and some of the factions in the opposition ... for the election to be held on September 4," said Zeev Elkin, an influential member of the Netanyahu´s Likud party.

"If the prime minister makes a decision on Sunday that we are going for it, then we can do it very quickly," he told Israel Radio, adding that he had already submitted a bill for the dissolution of the Knesset, which will discuss it next week.

The last time an Israeli government completed a full four-year term was when Menachem Begin led the country from 1977-1981. Many politicians thought Netanyahu´s coalition, which bonds religious and right-wing parties, would last the course.

However, Netanyahu looks eager to cash in on a raft of promising polls and seek an election that should consolidate his grip on power, with the country seemingly happy with his stewardship of the healthy economy.

POPULAR PRIME MINISTER

An opinion poll in the Maariv daily on Thursday showed Netanyahu´s Likud winning 31 seats in the 120-member parliament, a rise from its current 27, with the centre-left Labour party taking 18, making it the next biggest party in the legislature.

The poll showed centrist Kadima, which won most seats in the last elections in 2009, dropping from 28 to just 11, the same as the fledgling party of Yair Lapid, a popular television personality who has recently turned to politics.

As head of the biggest party, Netanyahu would be called upon to form a new administration, but he would need a number of partners to gain a parliamentary majority, a typical situation in Israel which has always been governed by coalitions.

Some secular politicians from across the political divide have suggested that Netanyahu should form a government of national unity and exclude the minority religious parties.

Such a move would enable Israel to hack away at some of the controversial privileges handed out to the ultra-Orthodox community over the past six decades, including rules making it easy for them to skip mandatory military service.

Once parliament is dissolved, the current administration remains in place and Netanyahu continues as prime minister until a new government is formed and approved by the Knesset after the coming election.

Another poll in the left-leaning Haaretz daily published on Thursday showed 48 percent of respondents thought Netanyahu was the most suitable candidate for prime minister and that he would leave his closest rivals trailing in his wake.

Labour´s Shelly Yachimovich was second, with 15 percent, and Shaul Mofaz, who last month took over as the head of Kadima from Tzipi Livni, trailed in third place with a meager six percent.

The same survey showed the majority of Israelis disapproved of tough comments last week by former spy chief Yuval Diskin, who accused Netanyahu and Defence Minister Ehud Barak of forming a belligerent, "messianic" duo unfit to tackle Iran.

The poll said 51 percent of respondents disagreed with Diskin, while just 25 percent supported his comments.

Barak looks set to be a big loser in any early vote, with polls showing his recently formed group, which splintered from the Labour party, winning no seats in the next parliament.

(Reporting by Ori Lewis; editing by Jeffrey Heller) (© Thomson Reuters 2012. 05/03/12)