If Prime Minister Ehud Olmert changes the criteria for deciding whether a Palestinian murderer can be released from jail, he will face a united front of opposition from Shas and Israel Beiteinu, Shas chairman Eli Yishai told The Jerusalem Post on Monday. Yishai's associates said he spoke to Israel Beiteinu chairman Avigdor Lieberman and they decided to fight the change together. Olmert did not invite representatives from either party to a meeting he convened on Monday to consider whether to change the current policy of not releasing prisoners with blood on their hands. Political sources said Olmert decided against inviting Shas and Israel Beiteinu officials because he knew they would oppose any decision and because he knew that he would have a majority in the cabinet to change the criteria without the support of Shas and Israel Beiteinu ministers. "I hope that with the right kind of struggle, we can succeed in preventing the changes," Yishai said. Yishai said that if Jewish murderers of Arabs such as Ami Popper would be released from jail as part of a prisoner exchange, he would be more likely to support it. But Shas is not unified in its opposition to a future prisoner exchange. Ministers Ariel Attias and Yitzhak Cohen are more willing to support a prisoner exchange for kidnapped soldier Gilad Schalit. "I want Gilad Schalit home," Cohen said. "If Gilad Schalit doesn't come home, we will have blood on our hands." Lieberman said he opposed changing the criteria, because it could lead to more kidnappings. None of the prisoner exchanges in the past proved worthwhile, he said. The Likud faction decided to oppose making the criteria more flexible. It said that when releasing terrorists, the government must consider the ramifications on the security of the citizens and avoid encouraging additional kidnappings in the future.