Greek conservative party leader Antonis Samaras gave a written commitment on Wednesday to implement a punishing new austerity package, a condition for Athens to get a second EU/IMF bailout and avoid national bankruptcy.

His New Democracy party is leading in opinion polls, meaning that Samaras is the frontrunner to become the next prime minister after elections expected in April.

In his letter to the Greece's international lenders, Samaras said he would stand by the conditions of both Greece's original 2010 bailout, the MoU, and the latest 130 billion euro rescue, the MEFP.

If Nea Demokratia wins the next election in Greece, we will remain committed to the Program's objectives, targets and key policies as described in the MoU/MEFP, he wrote, using the Greek name of his party.

But he added: Policy modifications might be required to guarantee the full Program's implementation.

The party released a copy of the letter.

Parliament approved the new package of pay, pension and job cuts in the early hours of Monday, as rioters burned down or otherwise wrecked almost 100 buildings in central Athens.

Samaras signalled during the debate that he might seek to renegotiate the deal with the European Union and International Monetary Fund, deepening EU suspicions that Greece would not fully implement its tough terms.

Samaras sent the letter shortly before a telephone conference call by the Eurogroup of euro zone finance ministers later on Wednesday.

However, Eurogroup Chairman Jean-Claude Juncker already called off a face-to-face ministerial meeting scheduled for Wednesday, partly due to the failure by Samaras to provide the undertaking in good time.

This appeared to reduce chances of the bailout being approved by euro zone finance ministers on Wednesday.

(Reporting by Renee Maltezou and Dina Kyriakidou; editing by David Stamp)