TEL AVIV—Prime Minister Benjamin Netanyahu´s Likud Party introduced a bill to dissolve parliament and advance the elections to this year from next, taking advantage of the Israeli leader´s commanding lead in public-opinion polls and a fractured opposition.

The early vote, which Israeli media said would be held on Sept. 4, is one of several developments that have scrambled calculations about the timing of any possible pre-emptive Israeli strike against Iran´s nuclear program.

As the West looks for a diplomatic resolution to the standoff with Iran through multilateral talks and economic sanctions, the expected Israeli elections are seen by some observers as representing another possible grace period for a potential attack.

"In an election all bets are off" after an attack, said Mitchell Barak, a pollster and ex-aide to Mr. Netanyahu. "You can´t be fighting a war and running an election at the same time."

Mr. Netanyahu´s Likud Party would get 30 of the 120 seats in Israel´s parliament and a 12-seat advantage over the next largest party if the elections were held in early September, a poll published in the daily Yediot Ahronot newspaper said this week. Likud now has 27 seats. Likud´s election bill is likely to pass.

Mr. Netanyahu is expected to campaign on a hawkish policy toward Iran to enhance his tough security image. But one senior Israeli official said Israel was unlikely to strike Iran at least until talks with the five permanent members of the United Nations Security Council and Germany are exhausted. Talks are set to continue May 23 in Baghdad.

However, in response to the suggestion in a Facebook chat that a caretaker government would lack the legitimacy to stage a strike with "far-reaching implications," Defense Minister Ehud Barak insisted its policy toward Iran wouldn´t waver.

"The executive branch continues as usual," he wrote. "Therefore elections will not influence the considerations of the professional level as far as the Iranian conundrum is concerned.´´

Western governments continue to oppose Iran´s nuclear program, which Iran says is aimed at producing energy, but they suspect has military aims. They are hopeful that tighter sanctions set to begin on July 1 will soften Tehran´s stance.

Mr. Netanyahu initially dismissed the talks as allowing Iran to stall for more time, but this week he dispatched Israel´s national-security adviser to Europe to discuss the progress of nonproliferation talks.

The senior Israeli official said it was still too early to tell whether or not the Iranians are serious about reaching a negotiated solution. "We think that in these negotiations with Iran, the Iranians will not show their cards until the very last moment," the official said. "It will take some time to know what they really want, and whether they want to reach a deal."

Many people believe any attack could jeopardize Mr. Netanyahu´s electoral advantage. Most Israelis oppose a lone pre-emptive attack on Iran because they view it as potentially resulting in a regional war and further Israeli isolation, polls show.

Despite his reputation as a security hawk, Mr. Netanyahu has never begun a broad military operation during his six years in office over two terms, and many believe that wouldn´t change during an election campaign.

"Clearly if he does early elections, it puts the Iran issue on hold because Netanyahu´s legendary caution would mean that he would not want the fate of his election hanging on the success of an pre- emptive attack," said David Makovsky, a fellow at the Washington Institute of Near East Policy.

One senior European Union diplomat says they have been following political developments in Israel closely but don´t feel early elections change their calculus. "We have got a strategy for dealing with Iran and we intend to carry on with that," he said.

Meanwhile, a rising chorus of security chiefs is openly criticizing the approach toward Iran by Mr. Netanyahu and Mr. Barak, the defense minister. In the past week, Yuval Diskin, the ex-director of the domestic Shin Bet security service, said he had no confidence in the two men and that a lone attack on Iran would backfire on Israel. Military Chief of Staff Lt. Gen. Benny Gantz said in a published interview last week he believed that Iran´s leadership was rational and unlikely to make a final decision to build a nuclear weapon.

Mr. Netanyahu, nicknamed "Bibi," "needs to take these remarks with caution," said Shlomo Madmon, a Likud activist. "If he attacks on his own with out the international community, he won´t be able to reach the point where Israel can win decisively....That would be a terrible mistake, and it would hurt Bibi and the party."

—Laurence Norman in Brussels contributed to this article. (Copyright © Dow Jones & Company, Inc.) 05/03/12)