Greek pension funds will not take part in a debt buy-back that is a key part of the country's international bailout, Greek Prime Minister Antonis Samaras said in a newspaper interview.

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

Greek pension funds hold more than 8 billion euros out of a total 63 billion euros of Greek bonds held by private investors.

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

(Reporting by Renee Maltezou; Editing by Ralph Gowling)