An anti-austerity protester stands next to riot police at the Greek Parliament on Monday during a rally against the government’s agreement with its creditors. (Emilio Morenatti/Associated Press)

Greek Prime Minister Alexis Tsipras scrambled Tuesday to hold his government together a day after striking a cash-for-cuts deal with European creditors that some within his radical leftist party consider a grievous betrayal.

In an interview on state television Tuesday night, Tsipras promised he would not resign, and defended the bailout agreement reached with creditors Monday after months of bitter talks as the best available choice for saving Greece’s deeply troubled economy. But he also portrayed himself as a man with no good options.

“I signed a deal I do not believe in, yet I have to implement,” he said.

Many in his own ranks disagree, and on Tuesday they launched an open rebellion. With a critical vote expected in Parliament on Wednesday, Greece’s largest unions will take to the streets to demand he renege on the deal. Dozens of members of his party, the radical leftist Syriza, have threatened to buck the government and vote against it.

Greek Energy Minister Panagiotis Lafazanis, who leads a hard-line leftist faction within Syriza, said in a statement Tuesday that the country’s creditors had “acted like cold-blooded blackmailers and economic assassins.”

Yet he also took indirect aim at Tsipras, calling on the prime minister to tear up the agreement, which Lafazanis described as a violation of the party’s ideals.

Even if Tsipras can pass the deal in Parliament, as expected, Lafazanis vowed that the Greek people would “annul it through their unity and struggle.”

The revolt reflected Tsipras’s awkward and increasingly tenuous position. He is a leader who has defined himself by his bare-knuckled fight against Europe’s dogmatic devotion to austerity.

But he now must sell a deal that is laden with pension cuts, tax increases and other measures that are widely regarded here as punishment for Greece’s temerity in taking a stand against the continent’s political heavyweights. In exchange for the fresh dose of austerity, Greece is set to receive a desperately needed $96 billion bailout, its third in five years.

Had Tsipras not signed the eleventh-hour deal on Monday, Greece probably would have been ejected from the euro zone, and its already crippled banking system almost certainly would have collapsed.

Both of those dire scenarios still loom as possibilities, especially if Tsipras does not win the Parliament’s endorsement of the deal in a vote expected Wednesday evening.

Political observers say such a rejection is unlikely. But with his party splintered, Tsipras will most likely need support from opposition parties to win backing for the agreement, raising questions about the viability of a government that controls 162 seats in the 300-member Parliament.

Dimitris Tsiodras, a spokesman for the opposition Potami party, said his group will support the agreement “to avoid catastrophe.”

But he said that after the vote, it will be up to Tsipras to build a new, workable majority, and he suggested that the prime minister try to “form a broad coalition with the pro-European parties.”

The possibility of a national unity government is one way out of Tsipras’s domestic dilemma. But it is not a course that is likely to sit well within Syriza, a coalition of radical leftists that came to power in January with a mission to revolutionize the country’s sclerotic politics.

Instead of a government overhaul, Tsipras on Tuesday appeared to be focused on minimizing losses within his current coalition, which includes both Syriza and the populist right-wing Independent Greeks party.

In a statement that reflected the murky politics of the moment, Independent Greeks leader Panos Kammenos said he will continue to back the government. But he also indicated that there are limits to his support and that he will not vote for elements of the bailout deal that he considers especially draconian.

Syriza officials, meanwhile, sought to pull the party’s members into line, with parliamentary spokesman Nikos Filis arguing that rebellion amounted to complicity in “a coup” engineered from Brussels.

Even as the divisions in Athens were laid bare, new rifts opened on the creditors’ side, as well.

British Chancellor of the Exchequer George Osborne said Tuesday that he would strongly oppose any attempt to force his country to help fund short-term loans to Greece, telling reporters in Brussels that “the euro zone needs to foot its own bill.”

The comments came as finance ministers from across Europe gathered to try to piece together a plan to keep Greece from defaulting on billions of euros’ worth of loans that are due Monday. The process, said Jeroen Dijsselbloem, leader of the euro-zone finance ministers, is “full of traps and snares” because of various legal and logistical obstacles.

A copy of an International Monetary Fund report, meanwhile, gave new credence to the Greek government’s demand for debt relief.

The report concludes that economic conditions in Greece have deteriorated so rapidly that the country requires “debt relief on a scale that would need to go well beyond what has been under consideration to date.” The report suggests a 30-year grace period.

European creditors have fiercely resisted the idea of debt relief, conceding only that they may be willing to discuss the issue at an undetermined future date — and only once Greece implements the creditors’ demands.

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