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.
Greece's Deputy Prime Minister has said the government might be open to calling off Sunday's referendum on a deal proposal by its international creditors, saying it was a political decision.
Speaking on state television, Yannis Dragasakis said the government decided on the referendum "and it can make a decision on something else."
It was unclear, however, how that would be possible as Parliament has already voted for it to go ahead.
Dragasakis also confirmed that Athens had asked the International Monetary Fund for an extension of the 1.6bn Euros payment due on Tuesday.
The bailout programme Greece has relied on for five years expired at midnight Tuesday and the country failed to repay the loan due to the IMF, deepening fears over whether it will be able to remain in the Eurozone.
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!'