Greek members of parliament are debating through the night ahead of a vote on a new bailout agreement.
The proposed deal involves tax rises and spending cuts in return for a third international bailout of about €85bn (£61bn).
Prime Minister Alexis Tsipras has said he is confident he will win the vote, but some senior members of his Syriza party are defying the government.
The debate itself was preceded by hours of often angry exchanges in parliament.
Mr Tsipras needs MPs to vote for a Memorandum of Understanding (MoU) to be adopted before eurozone ministers can endorse the draft deal worth about €85bn (£61bn; $95bn).
The eurozone ministers meet later on Friday.
The next crunch deadline for Greece is then 20 August, when it must repay about €3.2bn to the European Central Bank (ECB).
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In two prior votes on bailout reforms, Mr Tsipras faced rebellions from his own party with more than 30 of Syriza’s 149 MPs refusing to approve the latest tax increases, pension cuts and market reforms.
On Thursday, the bill was argued over in committee discussions and procedural wrangling for about nine hours, and the plenary debate did not start until well after midnight.
The leader of Syriza’s far-left faction, former energy minister Panagiotis Lafazanis called for a new movement to fight the deal.
The government said he had clearly decided “to choose a different path from that of the government and Syriza”.
It has defended the controversial new programme as tough but essential if the country is to avoid financial collapse.
Analysis: BBC diplomatic correspondent Paul Adams in Athens
Once again, the Greek parliament is the scene of long, passionate discussions, destined to go on all night. Earlier, during committee discussions, emotions were already running high. Now, as MPs wrangle over procedure, the main debate hasn’t even started. It’ll be many hours before the bailout bill comes to a vote.
With the main opposition parties generally supporting the bill, the outcome is not seriously in doubt. Parliament will approve an astonishing array of reforms which are likely to affect almost every aspect of economic life in Greece. Farmers will lose subsidies and see their rates of tax double. The self-employed will also be hit hard. There’ll be pension reform, too, and a review of Greece’s entire welfare system. The scope is breathtaking.
But getting all this through parliament will come at a cost. Mr Tsipras, who once vowed to resist any more austerity, faces a rebellion among hardline members of his own Syriza party. They’re threatening to break away and there’s already talk of fresh elections in the autumn.
The rebels, including parliamentary speaker Zoe Konstantopoulou and former finance minister Yanis Varoufakis, insist the government should make good on its electoral promise to reverse spending cuts and tax rises.
However, lawmakers are expected to approve the MoU by a comfortable margin with the help of opposition parties.
Meanwhile, the International Monetary Fund (IMF) urged Greece’s European partners “to make decisions on debt relief that will allow Greece’s debt to become sustainable”.
Senior IMF official Delia Velculescu said the organisation “will make an assessment of its participation in providing any additional financing to Greece once the steps on the authorities’ programme and debt relief have been taken”.
Her comments followed a meeting earlier this week with Greek and EU financial officials in Athens.
On Thursday, data showed the Greek economy grew by 0.8% in the second quarter of the year, confounding expectations of a steep contraction.
Until the figures were released, the economy had been forecast to shrink again this year by between 2.1% and 2.3%.