In an attempt to generate stronger participation in its key government bond buyback program, Greece on Monday extended the deadline for banks, funds and investors who own its debt to declare whether they will sell their holdings back at a heavy discount.The public debt management agency, PDMA, said bondholders now have until 1200 GMT (7 a.m. EST) on Tuesday to make up their minds.The program aims to cut some (EURO)20 billion ($25.81 billion) from the crisis-hit country's debt load and ensure it continues to get its international bailout loans. The original deadline expired on Friday, with Greece's largest banks saying they would participate.The government plans to spend about (EURO)10 billion in European funds on the buyback, offering between 30 and 40 percent of the bonds' face value. The bonds were trading at even lower prices than that on the secondary market, and Athens hopes investors will leap to the offer as many bought the bonds at less than half that price amid the political uncertainty that plagued Greece in the summer.PDMA head Stelios Papadopoulos insisted Monday that bondholders are being offered a good deal, and said efforts will continue to get the country's bloated debt back to a manageable course."Investors should bear in mind that even if Greece accepts all bonds tendered in the Invitation, it will continue to engage with its official sector creditors in considering further steps to put its debt on a sustainable path," he said. "Future measures may not involve an opportunity to exit investments in (designated Greek bonds) at the levels offered for this buyback."Government officials in Athens refused to comment on local media reports that the face value of bonds offered for sale so far has reached between (EURO)26 billion and (EURO)27 billion.Greece's financial crisis started three years ago when it admitted its budget deficit would be more than three times bigger than forecast. After it became impossible to raise money on the international bond markets, the country came to depend on rescue loans from its European partners and the International Monetary Fund, adopting harsh austerity measures to secure the funds.The hugely unpopular cutbacks contributed to a recession that has wiped a fifth off the country's output since 2008, while unemployment is at 26 percent - the worst in decades.Greece is hoping on Thursday to receive a (EURO)34 billion rescue loan installment, after a six-month delay caused by two national elections and long-dragging negotiations with the EU, IMF and European Central Bank over further demanded cutbacks. Although Athens has now adopted the spending, welfare and income cuts - coupled with new tax hikes - to get the money it still has to tie up the debt buyback over the next few days and table new tax laws on Tuesday.EU Commission spokesman Simon O' Connor insisted Monday that success of the bond deal is "an integral part" of last month's agreement to trim the Greek debt - which is set to reach 190 percent of GDP next year - and unfreeze the bailout cash."We are confident that there is still scope for additional tenders by domestic and international investors," he said.Greece's biggest banks have said they will participate in the buyback, without specifying to what degree. Domestic lenders have already been clobbered earlier this year by Greece's write-off on bonds held by private sector investors, but need the buyback to succeed as most of the forthcoming bailout funds are earmarked for their recapitalization.The Greek banks hold about a quarter of all the eligible bonds, which have a total face value of (EURO)63 billion. International hedge funds own an estimated (EURO)15 billion to (EURO)25 billion.Prime Minister Antonis Samaras was upbeat Sunday on the deal's prospects."I am convinced that by Monday or Tuesday, one will be able to say with relative certainty that things have gone very well," he said.