Greece must conduct the deal by December 13, before it receives more than 30 billion euros ($39 billion) in bailout payments from the euro zone and the International Monetary Fund.

Athens has said it is vital the buy-back is successful, but it must attract enough interest from bondholders, who need to decide whether to participate in the process, to ensure the country's debt is deemed viable in the coming decade.

"The debt buy-back does not concern the pension funds," Samaras was quoted as saying in an interview with Sunday's Proto Thema newspaper.

"We wouldn't erase the debt even if we took the funds' bonds. These are seen as arrears of the state to itself."

Greek pension funds hold more than 8 billion euros out of a total 63 billion euros of Greek bonds held by private investors. Greek banks are estimated to hold nearly 17 billion euros.

Most of their capital has already been wiped out by a debt cut in March and they must be recapitalized with more than 40 billion euros in bailout funds.

The government is expected to unveil the terms of the deal on Monday before a meeting of euro zone finance ministers. So far, international lenders have agreed the bonds would not be purchased for more than the closing price on November 23.

On the secondary market, Greek bonds eligible under the buy-back ranged from 25.15 to 34.41 cents in the euro at the close of trading on that date, according to Reuters data.

Greece aims to cut its debt by spending about 10 billion euros from its rescue package on the buy-back scheme.

Samaras said that Greek banks would benefit from the voluntary debt buy-back deal, since they held Greek bonds at lower prices on their books.

"The banks won't lose out because (the bonds) on their books are down at a lower price," he said. "They won't lose any of their capital but will end up with more liquidity."

A senior Greek banker told Reuters last week that some of the country's banks held Greek bonds at 22-23 euro cents on their books. However, the banks together were likely to forego about 3-4 billion euros in interest payments over the next 10 years if they participated.

The deal is seen as a golden opportunity for hedge funds which have bought the bonds at rock-bottom prices.

In an interview with Sunday's Ethnos newspaper, Greek Finance Minister Yannis Stournaras said many bondholders would profit from the deal and reiterated that Athens would make every effort to attract wide participation.

"This program must succeed," he said. "There is a big part of bondholders who bought them recently, at very low prices, and will possibly estimate that their participation in the buy-back program will be profitable," he said.

(Reporting by Renee Maltezou; Editing by Andrew Roche)

• A Permanent Economic Emergency