Ehud Olmert officially resigned as prime minister of Israel on Sunday, but the woman who hopes to replace him, Foreign Minister Tzipi Livni, faces formidable obstacles in preserving the governing coalition. Labor, her main governing partner, is weighing a move to early elections.

Mr. Olmert, mired in corruption investigations, stepped down by handing a letter to President Shimon Peres. Under Israeli law, Mr. Olmert automatically became the head of an interim government until a new prime minister is sworn in.

Mr. Olmert?s party, Kadima, narrowly elected Ms. Livni on Wednesday as its new head. Kadima has expected her to become prime minister by forming a new government from the existing components, the largest of which, after Kadima, is Labor. But Ehud Barak, the defense minister and head of Labor, has numerous reservations about the plan.

Labor?s support is essential for Ms. Livni to move into the prime minister?s office. The other large party, the opposition Likud, disagrees fundamentally with the government?s approach to negotiating peace with the Palestinian Authority and with Syria. It has repeatedly said it has no interest in joining the government.

Mr. Barak?s hesitation ? made clear over the weekend when he declined an early meeting request from Ms. Livni and met first with the Likud leader, Benjamin Netanyahu ? may be as much tactical as substantive. And while he did meet her on Sunday night, it may also be personal.

Mr. Barak, the most decorated soldier in Israel, is believed to chafe at taking orders from Ms. Livni, a lawyer who entered politics nine years ago with no national security experience other than the required military service and two years in a low-level Mossad espionage job in Paris.

Mr. Barak?s associates and key Labor Party activists say, however, that his concerns are as much about the future of the country and his party as about himself.

?This is not a game,? a close associate of his said, speaking on the condition of anonymity because he was not authorized to speak publicly. ?We are at a point in Israel?s history where major decisions have to be made. Barak thinks Livni is not ripe. She could be a good foreign minister or justice minister, but to be prime minister takes more.?

At the same time, polls show that if elections were held now, Mr. Netanyahu, a former prime minister, might win. Mr. Barak, also a former prime minister, may think he can overcome that present advantage and prevail in an election campaign.

Mr. Barak also worries that Ms. Livni will form a government that includes Labor and then, riding the prestige of the office, call elections in a few months, rather than wait for the scheduled elections in 2010. He wants assurances that the government will remain for the full term, the associate said.

Mr. Barak?s hesitations also grow out of the Labor Party?s identity and potential. Labor ruled for Israel?s first 30 years, and many of its members are still looking for a way back to the role that they consider their due.
Kadima activists say they are stunned. They retort that Mr. Barak insisted that Mr. Olmert make way for an untainted prime minister. Now that Mr. Olmert has done so, Mr. Barak is talking about new elections.

Nahum Barnea, a political columnist for the newspaper Yediot Aharonot, wrote of it this way on Sunday: ?The old Jewish joke tells about a bridegroom, who demanded, a minute before stepping under the wedding canopy, that the bride be undressed for his sake. One does not say no to a bridegroom. She was undressed for him, and then he said: I don?t like her nose.?

Such wedding analogies raise the question of whether the men who have long ruled Israel, at least since Golda Meir left office in 1974, are uncomfortable with a woman, as several commentators have suggested. If Ms. Livni becomes prime minister, all three branches of government will for the first time be led by women. The chief justice and the speaker of Parliament are women.
That can happen only if Mr. Peres asks Ms. Livni to form a government, a step expected on Monday. She would have up to 42 days; if she fails, elections would follow three months later. But some officials say that Mr. Barak and Mr. Netanyahu met over the weekend to agree on an early date for elections. If Parliament sets that date by law, Ms. Livni?s efforts to become prime minister without facing the voters and then run as the incumbent would come to an end.