The official said Thursday that Greece's international debt inspectors have discovered that a gap of around €15 billion remains between debt relief provided by banks and other private investors and a second, €130 billion bailout.

The official said the gap could be filled by more bailout loans from the eurozone or by eurozone central banks or publicly owned banks like France's Caisse de Depots taking a loss on their Greek bondholdings.

The official was speaking on condition of anonymity because of the sensitivity of the matter.

The European Central Bank and national central banks are estimated to hold €50 bilion to €55 billion in Greek bonds.