JERUSALEM — Israel's Defense Minister Ehud Barak said on Monday he was quitting politics, a surprise decision that deepens uncertainty over how Israel will confront Iran's nuclear program.

Barak's political fortunes appeared to be on the rise after Israel's eight-day Gaza offensive ended in a truce, but polls predicted his centrist party, a junior partner in right-winger Benjamin Netanyahu's government, would win no more than four seats in Israel's 120-member parliament in a Jan. 22 election.

A former head of the center-left Labor Party, Barak has insisted he and Netanyahu have been united on policy toward Iran, an issue that has often put the prime minister at odds with President Barack Obama.

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But as the only centrist member of the governing coalition of right-wing and pro-settler parties, Barak has frequently visited Washington for talks with top U.S. officials and had criticized Netanyahu for airing differences with the United States.

At a hastily called news conference, he said he would not be a candidate in the national ballot that Netanyahu's Likud party is forecast to win.

He said he would remain in his post until a new government was formed in about three months' time, signalling his decision would have no immediate effect on Israel's calculations on how best to curb Iran's nuclear ambitions.

"The Iranian issue remains very important, even after I leave my position in three months. It will remain a central issue on the agenda," said Barak, who was often seen as a moderating force in considering possible military action against Iran.

The 70-year-old ex-general said he wanted to spend more time with his family. Politics, he said, "has never been a particular passion of mine, and I feel there is room to allow other people to serve in senior roles in Israel."

Barak said he would be prepared to offer advice to the next prime minister, if asked, remarks that swiftly raised questions in Israel over whether he might consider serving in the next government as a political appointee.

"As long as my advice is asked for and held in high regard, I will make it available to the prime minister and to the heads of the establishment, on any defense or diplomatic issue," he said.

Barak has been defense minister since 2007 and served as prime minister from 1999 to 2001, taking time out from politics after he lost the election to the Likud's Ariel Sharon.

In a statement, Netanyahu said he "respects Defense Minister Ehud Barak's decision and thanks him for his cooperation in the government and highly appreciates his long-standing contribution to the security of the state."

The Hamas movement ruling Gaza saw Barak's decision to quit as proof that this month's Israeli assault on the enclave was a disaster.

"This is evidence of the political and military failure that the government of Netanyahu and his defense minister suffered," said Hamas spokesman Fawzi Barhoum.

Israel has called its offensive a success, saying it destroyed most of Hamas's long-range rocket arsenal and killed the Islamist group's top militants.

IRAN STRIKE

A former commander in an elite commando unit, Barak tried unsuccessfully to make peace with both the Palestinians and Syria during his time as prime minister.

He was at the forefront of Israel's campaign for stronger international sanctions against Iran to halt what Israeli and Western leaders fear is a drive to produce nuclear weapons, allegations Tehran denies.

He has cautioned that Tehran was nearing a "zone of immunity" that would put deeply buried and fortified nuclear facilities out of reach of Israel's military capabilities, stoking international concern it could opt to strike Iran.

But last month, Barak told Britain's Daily Telegraph newspaper that an immediate crisis was avoided when Iran chose to use more than a third of its medium-enriched uranium for civilian purposes earlier this year.

He told the paper that the decision "allows contemplating delaying the moment of truth by eight to ten months."

Listing his achievements, Barak said he had led the defense establishment and the Israel Defence Forces through a rehabilitation after the second Lebanon war in 2006 and the building of capability to deal with the threat from Iran.

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Barak's decision to call a news conference, with only two hours' notice, had touched off speculation he might announce the formation of a new centrist bloc to challenge Netanyahu's frontrunning Likud in the upcoming ballot.

Former Foreign Minister Tzipi Livni and ex-Prime Minister Ehud Olmert have been widely touted as possible candidates to lead such a bloc. Neither has announced their intentions, with only Livni widely expected to run.