Story highlights Police estimate 35,000 people turned out for a peaceful protest in Athens

A 31.5 billion-euro bailout installment is due from the European Union and IMF

The Greek parliament is required to pass new austerity measures beforehand

Local media say the vote will be a cliffhanger, with narrow passage expected

The nation of Greece has come to a screeching halt again.

Unions have called for a 48-hour general strike beginning Tuesday ahead of an anticipated vote by the Greek government on yet another round of austerity measures the following day.

Protesters filed past parliament, their banners and Greek flags flapping in the air over their heads.

Greek media are expecting a cliffhanger in parliament late Wednesday night, with passage of the austerity measures by just a handful of votes.

If legislators do not pass the measures, it will endanger the payout of the next international bailout installment of 31.5 billion euros, which the government desperately needs to stay in operation. Without the funds, it says it will run out of money by mid-November.

But Greeks are furious about the effects of multiple rounds of belt-tightening, which have resulted in cuts to pensions and pay and seen unemployment in Greece's fifth year of recession soar to over 25%.

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More than one-fifth of the population could face poverty, defined as a family of four on an income of 13,842 euros (about $17,500) per year, state news agency AMNA has reported.

Critics of austerity have called for economic stimulus programs instead, like those implemented in the United States.

The two-day general strike will shut down transportation across the country, including ships and taxis, said AMNA, which is joining the strike along with other media outlets for four and a half hours Tuesday.

Hospitals are striking both days, and pharmacies will close all day Wednesday. Government offices are shuttering for the extent of the strike.

About 35,000 demonstrators turned out in Athens, Greek police spokesman Panagiotis Papapetropoulos said.

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The street protest remained peaceful, without any of the disturbances that have marred other demonstrations in recent months.

Wednesday is expected to draw the larger crowd of demonstrators as the vote approaches.

If Greece is to stay the course laid out by the so-called troika -- the European Commission, the European Central Bank and the International Monetary Fund -- more budget cuts will be necessary, as the country's debt woes are worse than previously believed.

Recent budget projections for the Greek government exceed the worst-case scenarios envisioned by international lenders when they agreed to a bailout, according to a Financial Times report published by CNN.

The hardship many Greek people are suffering has resulted in dogged opposition in parliament to deeper cuts, including within the ruling coalition.

The Democratic Party of the Left, or DIMAR, one of three parties making up the coalition headed up by Prime Minister Antonis Samaras, has said it will abstain in the vote on the new round of austerity measures, turning in blank ballots. But it plans to vote Sunday to approve the government's new budget.

Samaras' own center-right New Democracy party is expected to vote in favor of the package.

Although the third coalition member -- the socialist party Pasok -- supports the cuts, individual party members have come out against them and could defect, putting the vote in jeopardy.

Radical leftist party Syriza, bitterly opposed to austerity and closely connected to Greek unions, calls on its website for Greeks to demonstrate against the "rape" of democracy and the dashing of the hopes of the people.

Samaras warned that if the measures don't pass and international funds don't arrive, the nation could plunge into chaos. He is pushing for Greece to receive more than the 31.5 billion euros expected in the latest installment "so that there is a significant effect on the real economy."

Greece, and particularly Athens, has seen repeated street demonstrations against the austerity measures imposed on the nation, some of which have turned violent.