By Jeffrey Heller
JERUSALEM (Reuters) - Prime Minister Benjamin Netanyahu is expected to announce on Sunday an early general election on September 4, a spokesman for his Likud party said, a ballot likely to strengthen his hand as Israel confronts Iran's nuclear ambitions.
The next national vote was not due until October 2013, but new legislation that might force ultra-Orthodox Jews to serve in the military and an upcoming budget debate have threatened to unravel a governing coalition of religious and nationalist parties once seen as one of the most stable in Israel's history.
A Netanyahu victory, two months before the U.S. election, is widely seen in Israel as giving him a measure of leverage over Barack Obama on the Iranian and Palestinian issues while the U.S. president is still engaged in his own race and wary of alienating pro-Israeli voters.
Netanyahu and Obama have had a thorny relationship and the right-wing Israeli leader has come under pressure from Washington not to take unilateral military action against Iran's uranium enrichment facilities.
The Likud spokesman said Netanyahu was expected to tell a party convention later in the day that he would ask parliament to dissolve and set a September 4 election date.
Opinion polls show Likud will easily come out on top of the national ballot, giving Netanyahu a renewed mandate to tackle what he has described as the most important challenge facing his country - the prospect of a nuclear-armed Iran.
Parliament was due to convene on Monday and vote on a coalition-backed resolution of dissolution. Netanyahu and his government would remain in office until a new administration is sworn in after the election in four months' time.
Israeli leaders have insisted the election campaign would have no impact on their decision-making on Iran. Israel, believed to be the Middle East's only nuclear power, says Iran aims to produce an atomic bomb. Iran says its nuclear program is peaceful.
"Netanyahu does not hide his intention to strike Tehran's nuclear sites before they become immune to attack," commentator Ron Ben-Yishai, referring to deeply buried atomic facilities, wrote in Israel's popular Yedioth Ahronoth newspaper.
"Hence, his decision to call early elections when his position on this issue is so clear and consistent shows confidence that Israel's public is behind him, thereby granting more credibility to the Israeli threat," he wrote.
But Netanyahu has been urged by Washington and other world powers to allow beefed-up international sanctions on Iran to bite. He has voiced pessimism about the outcome of international nuclear talks with Iran due to resume in Baghdad on May 23.
While opinion polls have shown strong support for Netanyahu's leadership, they have also indicated a wide majority of Israelis either oppose an Israeli strike on Iran or would favor an attack only if it were carried out with U.S. agreement.
Some former Israeli security chiefs have also criticized Netanyahu's hawkish stance. His former internal security chief, Yuval Diskin, accused both him and Defence Minister Ehud Barak of having a "messianic" policy toward Iran.
On Friday, Barak said Iran's nuclear strategy could eventually allow it to build an atomic bomb with just 60 days' notice. The remarks elaborated on long-held Israeli concerns that Tehran is playing for time as it engages in negotiations aimed at curbing its uranium enrichment.
(Additional reporting by Allyn Fisher-Ilan; editing by David Stamp)