ATHENS (Reuters) - Greece's finance minister expressed satisfaction on Sunday that the country's banking system "passed successfully" the ECB's stress tests, noting that Athens still has a buffer of 11.4 billion euros at its bank bailout fund. "It's extremely important that the reserves of 11.4 billion euros at the HFSF (Hellenic Financial Stability Fund) are left unused," Greek Finance Minister Gikas Hardouvelis said in a statement. (Reporting by Lefteris Papadimas; Writing by Renee Maltezou, Editing by George Georgiopoulos)