After the partial agreement with Germany, Greek PM had faced a heavy attack from rebels for capitulation to German demands. Greece's leftwing Prime Minister Alexis Tsipras faces a showdown with rebels in his own party on Tuesday furious at his capitulation to German demands for one of the most sweeping austerity packages ever demanded of a euro zone government. Just hours after a deal that saw Greece surrender much of its sovereignty to outside supervision in return for agreeing to talks on an 86 billion euro bailout, doubts were already emerging about whether Tsipras would be able to hold his government together, Reuters reported. The terms imposed by international lenders led by Germany in all-night talks at an emergency summit obliged Tsipras to abandon promises of ending austerity. Instead he must pass legislation to cut pensions, increase value added tax, clamp down on collective bargaining agreements and put in place quasi-automatic spending constraints. In addition, he must set 50 billion euros of public sector assets aside to be sold off under the supervision of foreign lenders and get the whole package through parliament by Wednesday. Tsipras himself, elected five months ago to end five years of suffocating austerity, said he had "fought a tough battle" and "averted the plan for financial strangulation". But to get the accord through parliament by Wednesday's deadline, he will have to rely on votes from pro-European opposition parties, raising big questions over the future of his government and opening the prospect of snap elections. Leftwing rebels in the ruling Syriza party, and his junior coalition partner, the right-wing Independent Greeks party, indicated they would not tear up election pledges that brought them to power in January. "We cannot agree to that," Independent Greeks leader Panos Kammenos told reporters after meeting Tsipras. "In a parliamentary democracy, there are rules and we uphold them." A meeting of the Syriza parliamentary group on Tuesday morning could see Energy Minister Panagiotis Lafazanis and Deputy Labor Minister Dimistris Stratoulis sacked over their opposition to the bailout. There may also be a battle over parliament speaker Zoe Constantinopoulou, an uncompromising leftwinger who also defied Tsipras over the bailout and who could create serious procedural obstacles for the package.