Parliament is expected to give a final green light late in the day to the belt-tightening plan required by the EU and the IMF, after backing it in principle in a first reading on Wednesday despite the country's biggest labor action in years.
But some ruling party MPs have warned they may vote against one of the bill's most controversial provisions, threatening to weaken the beleaguered government's narrow majority as it battles a debt crisis that is shaking global markets.
Thousands of police will be deployed through central Athens after black-clad youth clashed with riot police on Wednesday, pelting them with petrol bombs and chunks of marble during an anti-austerity march that drew more than 100,000 protesters.
Ships will be docked, ministries and schools shut and hospitals will work on skeleton staff in the second day of a 48-hour strike against plans to pile more taxes on austerity-hit Greeks and put tens of thousands of state workers on the road to redundancy.
"The protests will shake the government again, they will feel like an earthquake," said Ilias Iliopoulos, secretary general of public union ADEDY.
Protesters are set to rally in front of parliament from 0800 GMT (4 a.m. ET) and will try to stay on the square till late at night, while lawmakers vote on the bill.
Analysts expect the protests to continue unabated as Greeks of all walks of life have become increasingly angry at measures they feel only hurt the poorest while tax evaders and corrupt politicians remain unaffected.
But commentators see no other option for the ruling Socialists, who hold 154 seats in the 300-strong assembly, than to pass the measures, a key condition to convince the EU and IMF ahead of a crunch summit on Sunday that Greece deserves to keep getting the loans it needs to avoid bankruptcy.
"People sent a message on Wednesday that they have reached their limits and can't take any more austerity," said Theodore Couloumbis of the ELIAMEP think-tank.
"But these kind of protests cannot topple the government ... I don't see this happening now," he said.
The bill foresees an average income cut of about 20 percent for public sector workers, according to estimates by public sector labor unions, and reduces the tax-free income threshold.
It will make it easier for firms to cut payroll costs by reaching company-level wage agreements, which has particularly angered some ruling party lawmakers."
Prime Minister George Papandreou will hold a cabinet meeting at around 0900 GMT, ahead of the parliamentary vote and of Sunday's EU summit.