New doubts have been cast over eurozone efforts to rescue the Greek economy.
Credit ratings agency Standard and Poor's has warned it would treat as a default a French bank plan for a rollover of privately-held debt.
Bank stocks subsequently fell in Europe and the cost of insuring Greek debt against default continued to rise.
The European Commission has said the eurozone is expected to make progress on a new Greek bailout at 11 July talks, but will need extra weeks to finalise the role of the private sector in the rescue.
Amadeu Altafaj, spokesman for European Commissioner for Economic and Financial Affairs Olli Rehn, has refused to comment on the warning from Standard & Poor's.
'We are working on this private sector involvement so there is no decision taken yet,' Mr Altafaj told a news briefing.
Asked if a decision on the second bailout plan for Greece would be made at a eurozone finance ministers' meeting in Brussels next Monday, he said: 'We expect necessary progress in this meeting of the Eurogroup in order to have clarity about the main features of the successor programme.
'And then talks will continue to determine the precise modalities and scale of private sector involvement and additional funding from official sources, because one is linked to the other.'
Eurozone finance ministers had already indicated during a weekend conference call that it would take weeks for them to conclude negotiations, signalling that no decision was expected at their next meeting in Brussels next Monday.
German Finance Minister Wolfgang Schaeuble indicated that an agreement will likely have to wait until autumn. European diplomats suggested a deal could be concluded by September.
