Sources among the four rebellious Labor MKs praised the appointment of businessman Yoni Koren as Labor chairman Ehud Barak's new chief of staff Tuesday, but expressed doubt that he could help heal the deep rift in the ailing party. Koren will replace former Channel 2 director-general Shalom Kital, who tendered his resignation on Monday. A reserve Lieutenant-Colonel, Koren served as Barak's bureau chief when he was IDF chief of General Staff and foreign minister, but he broke a promise to appoint him to that position when he became prime minister in 1999. Although his main focus in the position will be on the day-to-day matters of the Defense Ministry, Barak could take advantage of Koren's long-standing relationship with Labor rebel MKs. But sources among the rebels said the rift in the party was already inevitable and even the world's best adviser could not fix Labor's problems. "Unfortunately, the problem is Barak himself and not one adviser or another," a rebel source said. "Yoni is very talented. He understands politics, foreign policy, gets along with people and he probably knows how to handle Barak better than anyone else. He could succeed more than anyone else, but in the end, he is still only an adviser." The rebel source continued. A team Barak appointed to reach out to the four rebel MKs sent them a letter last week. MKs Ophir Paz-Pines, Eitan Cabel, Amir Peretz and Yuli Tamir intend to respond to the letter on Wednesday. A source among the rebels said Kital's departure was further proof that Barak "is a man who is impossible to work for and with." But Barak's associates said Kital's departure was not personal and that the main reason he left his post was that Barak had started accepting Koren's advice on key issues over Kital's. The associates said that Barak proved his behavior was not as problematic as his reputation when he continued working with Kital even after Labor won only 13 seats in the February election with a campaign Kital managed. "That was a real test," the Barak associate said. "The fact that he didn't fire Shalom after the election shows that he is not such a bad guy."