A first set of reforms that focused largely on tax hikes and budget discipline triggered a rebellion in Syriza last week and passed only thanks to votes from pro-EU opposition parties.

The bill lawmakers will vote on late on Wednesday covers rules for dealing with failed banks and speeding up the justice system - two more conditions set by the euro zone and IMF to open negotiations on an 86 billion euro rescue loan.

The legislation is all but certain to pass, despite planned protests, after opposition parties said they would back it.

But with divisions in Tsipras' leftist Syriza party laid bare by last week's rebellion by 39 deputies, Wednesday's vote will be closely monitored to see if he loses even more support.

"We are making an effort to have fewer dissenters," Health Minister Panagiotis Kouroumplis told Greek TV, while Finance Minister Euclid Tsakalotos said it was crucial that parliament backed the deal so bailout talks could start on Friday.

But hardline Left Platform lawmakers from the Syriza party, who opposed last week's bill, said they rejected this week's law as well.

"A fast-track parliamentary debate and voting process of a bill which exceeds 900 pages has the taste of the most anti-democratic practices," they said in a statement, published on their website Iskra.gr.

Tsipras himself, who is associated with the moderate wing of his party, has publicly said he disagrees with measures demanded by Greece's euro zone peers and the IMF for talks to proceed on a third bailout to save the country from bankruptcy.

But after he made a U-turn by accepting a deal at the 11th hour to keep his country in the euro, he told party hardliners on Tuesday that they should face reality and back the package.

Together with his coalition partners from the right-wing nationalist Independent Greeks, Tsipras has 162 seats in the 300-seat parliament. But last week's rebellion cut his support to just 123 votes and government officials have said elections are likely in the autumn.

"We might go to elections, when this is needed," government spokeswoman Olga Gerovasili told a local radio, adding that this would not be helpful right now as the country prepares to negotiate the new bailout deal. "We are trying to bring the situation back to some sort of normality," she said.

European Economic and Monetary Affairs Commissioner Pierre Moscovici told reporters in Brussels that he was confident the parliament would adopt the bill. Creditor institutions were seeking to conclude talks with Greece on a third bailout in the second half of August, he said.

The government has said it hopes negotiations on the bailout deal can start this week and be wrapped up by Aug. 20.

PROTEST RALLIES

In first signs of a return to normality, Greek banks reopened on Monday and Athens paid debts due to the European Central Bank and International Monetary Fund. On Tuesday, Standard & Poor's upgraded Greece's sovereign credit rating by two notches.

But fresh austerity measures are hard to accept in a country whose economy has contracted by a quarter during five years of crisis and where unemployment is more than 25 percent. The main public sector union ADEDY, the communist-affiliated party PAME and anti-establishment groups have called rallies for Wednesday.

"We will continue our battle so that the new barbaric bailout does not pass and is overturned," ADEDY said in a statement.

Anti-austerity rallies last week briefly turned violent when masked youths hurled petrol bombs at police as lawmakers were debating the first bailout bill.

With mistrust among euro zone countries still high despite the deal struck last week to launch bailout talks, a senior German lawmaker in Chancellor Angela Merkel's conservative party warned Greece it would not get aid if it backtracked on reforms.

"We are keeping a close eye on whether Athens not only adopts the reforms, but also implements them," Gunther Krichbaum, chairman of the German parliament's Europe committee, told the newspaper Bild. "Greece must fulfil the conditions, otherwise the money cannot flow."

The bill will not include pension reforms curbing early retirement or increasing tax rates paid by farmers - a step strongly opposed by the conservative New Democracy party and many Syriza deputies.

The fact that these measures were not included in the bill aroused some media speculation that Athens was backtracking on reform commitments. Tsakalotos told lawmakers Greece had agreed with its lenders to deal with these issues during bailout talks.

The bill adopts into Greek law new EU rules on dealing with failed banks, imposing losses on shareholders and creditors of ailing lenders before any taxpayers' money can be tapped in.

That part of the bill is expected to pass more easily than the reform of the judicial system, which is similar to a law that Syriza had opposed before it came to power, and which hardline Left Platform lawmakers particularly oppose.

Greece's creditors say the measure is needed to speed up court proceedings and reduce their cost. Greek leftists say it violates rights to a fair hearing and could favour creditors and hurt workers in bankruptcy cases.

(Reporting by Costas Pitas, Angeliki Koutantou and Renee Maltezou; Writing by Ingrid Melander; Editing by Paul Taylor and Peter Graff)