Greek politicians are to vote later on austerity measures that have sparked nationwide strikes and the worst rioting in Athens for more than a year.
PM George Papandreou has said that only his 28bn-euro (£25bn) austerity plan will get Greece back on its feet.
The package is expected to be approved by parliament by a narrow margin, but correspondents say it is unlikely to bring an end to the unrest.
If it is not approved, Greece could run out of money within weeks.
Parliament is scheduled to finish debating the bill at 1300 (1100 GMT), with the vote taking place some time after.
Greek officials say 46 people were injured in the capital on Tuesday, including 37 policemen, after an anti-cuts rally turned violent.
Police used tear gas against groups of youths in the streets around parliament, and arrested at least 14 people.
The roads of the capital were left strewn with broken paving stones and other debris after the first day of a 48-hour general strike against the planned austerity measures.
Greece's austerity package and its implementation law must be passed in separate votes later on Wednesday and on Thursday for the next instalment of the country's 110bn-euro bail-out to be released by the EU and IMF.
If passed, European officials will also start to finalise the details of a second bail-out - worth an estimated 120bn euros - designed to help Greece pay its debts until the end of 2014.
The impact of the Greek vote would be felt worldwide, EU President Herman Van Rompuy said on Tuesday.
Petrol bombs
A Greek government defeat would send ripples of anxiety right across the eurozone, with Greece facing the prospect next month of becoming the first member state to default on its debts, says the BBC's Chris Morris in Athens.
Late on Tuesday, the newly-named IMF chief, Christine Lagarde, urged Greek politicians to unite to avoid a debt default, saying: "The country's destiny is at stake.
"If I have a message this evening about Greece, it is a call to the Greek opposition... to join in national unity with the party which is currently in power."
Thousands of protesters marched through Athens' traffic-free centre on Tuesday as public transport ground to a halt during the general strike.
Amid plumes of smoke and tear gas, anarchist rioters - some wearing gas masks - threw petrol bombs and bits of stone chipped from buildings as well as torching two communications vans.
One man was reportedly stabbed as fighting broke out between rival groups of protesters; some trade unionists tried to persuade anarchists to leave the square, saying their violent protests were only harming the demonstrators' cause.
More than 5,000 police officers were deployed to control the protests.
The strike halted most public services, closed banks and saw hospitals operating on skeleton staff while many flights, trains, buses and ferries were cancelled. Protesters blockaded the port of Piraeus, near Athens, which links most Greek islands with the mainland.
The unions are angry that the government's austerity programme will impose taxes on those earning the minimum wage, following months of other cuts which have seen unemployment rise to more than 16%.
Polls suggest that as many as 80% of Greeks oppose the austerity measures.
Recently appointed Finance Minister Evangelos Venizelos acknowledged that the cuts were "unfair", but said they were absolutely necessary, and called on all MPs to back them.
But the main opposition leader, Antonis Samaras of the New Democracy party, said the thinking behind the austerity package was flawed and that tax rates should be lowered rather than raised in order to stimulate the economy.
Mr Papandreou faces opposition from within the governing Panhellenic Socialist Movement (Pasok), with two MPs saying they may oppose the bill.
The party has a slim majority, with 155 seats out of 300 in parliament.
