The ECB is the central bank of Greece, but we are also the central bank of 18 other countries and we cannot bend our rules to suit the occasion. The Greek government can relieve funding constraints by pursuing policies which will open the way to disbursements by other Member States under the programme and, ultimately, restore market access.
Let me add that the ECB’s monetary policy stance is currently very accommodative. Greece also clearly benefits from this. BIS central bankers’ speeches  3