The head of Greece's bank rescue fund maintained on Thursday that Athens has a legal claim to 1.2 billion euros in the euro zone's bailout fund, a day after European officials rejected its request.

Athens had appealed for the European Financial Stability Facility to return 1.2 billion euros it said it had overpaid when it transferred bonds intended for bank recapitalization back to the Luxembourg-based fund this month.

But euro zone officials agreed on Wednesday that Greece was not legally entitled to the money, dashing Athens's hopes for a quick cash payment it needs to help avert potentialbankruptcy as early as next month.

In a statement on Thursday, the chief executive of the Hellenic Financial Stability Fund (HFSF), Anastasia Sakellariou, defended Athens's claim.

"We have brought to the attention of the EFSF that the unutilized bonds exceeded in value the difference between the total capital contributed and the total funds used for bank recapitalization and resolution," Sakellariou said.

"Consequently, a legitimate request has been put forward for differentiating and reinstating the amount of 1.2 billion."

The recapitalization in cash, rather than in EFSF bonds, was undertaken under the previous conservative-led government even though the HFSF still held 10.9 billion euros in EFSF bonds especially marked for that purpose.

Sakellariou said the allocation of the HFSF's resources was "appropriate based on prudent treasury management practices."