Some of Greece's biggest banks may have to shut and merge with their rivals, it has been claimed.
A European official told the Reuters news agency that Greece's four big banks - National Bank of Greece, Eurobank, Piraeus and Alpha Bank - could be reduced to just two.
European leaders are meeting on Sunday in a bid to strike a financial aid deal with Greece.
European Council President Donald Tusk has warned Greece that this week's deadline for a reform-for-loans deal is "final", after the country's Prime Minister was told to come up with new proposals by Sunday.
Speaking after today's summit of European leaders, Tusk said: "The stark reality is that we have only five days left... Until now I have avoided talking about deadlines, but tonight I have to say loud and clear that the final deadline ends this week."
Tsipras told reporters talks at the summit "took place in a positive climate" and said the process for a new Greek offer would be "extremely fast".
The Greeks have voted to reject the austerity terms demanded by eurozone creditors - so, what happens next?
Greeks have voted to reject the terms of an international bailout, putting it on the brink of a eurozone exit.
Greece's controversial Finance Minister Yanis Varoufakis has released a defiant statement of resignation entitled 'Minister no more!'