"The door is open to discussions," said French President Francois Hollande after crisis talks in Paris with German Chancellor Angela Merkel.

"It is now up to the government of Alexis Tsipras to make serious, credible proposals so that this willingness to stay in the eurozone can translate into a lasting programme."

With Greece's economy gasping for air, the authorities extended an eight-day bank closure until Thursday amid fears cash machines in the country were running dry.

The European Central Bank, which has been keeping Greek lenders afloat, meanwhile announced it would maintain a key financial lifeline to Greek banks, but raised the bar for them to access the emergency funds, Al Jazeera reported.

Greek Prime Minister Alexis Tsipras is to unveil his government's proposals on Tuesday at a hastily arranged emergency summit of the 19 eurozone countries in Brussels. He spoke to the German Chancellor earlier in the day regarding the new proposals.

Late on Monday, a Greek government source said that Tsipras had spoken to ECB chief Mario Draghi in efforts to reopen banks with assistance from the Frankfurt-based lender.

Tsipras also spoke to IMF chief Christine Lagarde "on the need to find a viable solution dealing with the real problems of the Greek economy", the source said.

For her part, Merkel said the conditions for a new Greek rescue package "have not yet been met".

"And that is why we are now waiting for very precise proposals from the Greek prime minister, a programme that will allow Greece to return to prosperity," said Merkel, adding that eurozone countries had already shown "a lot of solidarity with Greece".

The Netherlands' Prime Minister Mark Rutte said that Greece will have to accept deep reforms if it wants to remain in the eurozone.

Greece last week defaulted on a $1.8bln repayment to the International Monetary Fund but Lagarde said her organisation was "ready to assist Greece if requested to do so".

Tsipras, 40, insists that instead of the so-called Grexit, the creditors will now finally have to talk about restructuring Greece's massive 240 billion euro ($267bn) debt to them.