Greece announced it had extended until Tuesday a debt buyback offer, the success of which is key for it to receive bailout funding from the EU and IMF without which it could soon go bankrupt. \"We have decided to extend the invitation to offer designated securities for exchange to 11 December 2012,\" the head of Greece\'s PDMA debt management agency, Stelios Papadopoulos, said in a statement on Monday. Private holders of Greek sovereign bonds originally had to submit by Friday their offers to participate in the buyback, which offered them 32.2 to 40.1 percent of the face value of the securities. The PDMA statement said they now had until 1200 GMT on Tuesday to submit bids to participate in the buyback, which aims to cut Greece\'s debt by around 20 billion euros ($26 billion) and is vital to qualify for more financial aid from the European Union and International Monetary Fund. The head of the PDMA warned that any future offers to buy back debt may not be as advantageous to investors. \"Future measures may not involve an opportunity to exit investments (Greek sovereign bonds) at the levels offered for this buyback,\" Papadopoulos said. The IMF and the eurozone have agreed to release 43.7 billion euros in rescue loans in four instalments to enable Greece to avoid bankruptcy provided Athens carries out the bond buyback.