Hoping to bolster his position within the Labor Party but jeopardizing his place in the coalition, Defense Minister Amir Peretz said Thursday that he was joining the mounting calls for a state commission of inquiry into the war against Hizbullah. Peretz's decision puts him in direct opposition to Prime Minister Ehud Olmert, who called this week for two governmental commissions of inquiry rather than the broader and more authoritative investigation a state commission would conduct. "I will be willing to face any type of inquiry into my conduct during the war," said Peretz. "During this war, various failures were uncovered on a number of levels. We need to check and investigate them without compromise." Sources close to the prime minister said he was surprised by Peretz's decision, adding that it was likely to create a crisis over Labor's continued membership in the coalition. "It is not clear that this will be the straw that breaks the coalition," a source in the Prime Minister's Office said. "But the strain is certainly building." Sources close to Peretz said he hoped that his decision would not lead to the end of his partnership with Olmert. "He does not feel that this should be enough to oust Labor from the coalition," said an aide close to Peretz. "He hopes to remain in the coalition and to hold on to his position as defense minister for the foreseeable future." Since Olmert announced his plan Monday night, Peretz has vacillated between falling in line with the prime minister and joining the majority of Labor Party MKs, who have called for a state commission. A state commission of inquiry is the most authoritative forum for investigating the conduct of state authorities. It is headed by a Supreme Court justice and has the power to summon witnesses and dismiss senior officials. Peretz's decision does not bode well for the coalition, which is already on shaky ground following the refusal of three Labor MKs to support the government in a vote to cut the budgets of all ministries, except defense and education, to pay for the recent war in the North. "The Labor Party has once again proved its failure to be a dedicated, reliable member of the coalition," said coalition chairman MK Avigdor Yitzhaki (Kadima). "It proves the need to expand the coalition." Likud, Israel Beiteinu, NU-NRP and Shas have all been proposed as possible coalition partners; all of them would require that the coalition agreement be rewritten to accommodate more right-wing policies. The crisis over whether to bring in some of those parties is likely to take place after the next cabinet meeting, when ministers will voice their positions on Olmert's plan for multiple inquiry commissions, sources in the Prime Minister's Office said. At that meeting, Peretz will join Labor Ministers Ophir Paz-Pines and Eitan Cabel in voting against Olmert's inquiry commissions. It also seems likely that Education Minister Yuli Tamir, a longtime ally of Peretz, will vote against the PM. "Even if they all vote against Olmert's plan, it will still have a majority to pass," said one Kadima minister. "They are just doing it for the media... In the end, they are severely jeopardizing their relationship with Olmert, too." The Prime Minister's Office had no formal response to Peretz's decision, beyond saying that Olmert's proposal to establish three investigative committees, rather than a state commission of inquiry, would be brought to the next cabinet meeting, scheduled for Wednesday. Sources close to the prime minister said, however, that the move was clearly a political one aimed at nipping in the bud attempts inside Labor to unseat Peretz. The sources said there was "no chance" the cabinet would muster close to enough votes to vote down Olmert's proposal and pass a resolution calling for a state commission. Ministers Isaac Herzog, Shalom Simhon and Binyamin Ben-Eliezer, all of Labor, said they still felt that Olmert's plan was appropriate and that they did not feel a state commission of inquiry should be established. "They will listen and weigh what their fellow Labor [Knesset] members say, but it's unlikely they will change their minds," said a spokeswoman for Herzog. On Friday morning, Labor MKs will meet at the party's Tel Aviv headquarters to discuss the party's position on the inquiry issue. Two-thirds of the party's 19 MKs have voiced support for a state commission of inquiry, calling Olmert's plan a "fig leaf" and a joke. "There is widespread sentiment in the party that Olmert has gone too far with his inquiry plan and failed to take the opportunity to earn the public's trust with a real state commission of inquiry," said a senior Labor legislator. "If Peretz had not joined the party's sentiment on this... his leadership would have been in serious jeopardy." Peretz's position as party chairman has been called into question by a number of MKs, most recently MKs Ami Ayalon and Avishay Braverman, who announced they were joining together to run for the party leadership. March appears to be the earliest that a Labor Party primary could be held and Peretz officially challenged. "We will decide between us who will be No. 1 and who will be No. 2. We represent different policies, and we will bring change to the Labor Party," Ayalon said Wednesday. Also Thursday, a poll released by Israel Radio showed Braverman leading Peretz for the party leadership, with Braverman receiving 43 percent of the votes and Peretz 32%. "There is no doubt that the chairman's position in the party depends on how he acts over the coming week," Paz-Pines said. Herb Keinon contributed to this report.