Greek leaders are poised for a fresh round of talks to break the political deadlock and keep their country from bankruptcy and in the eurozone.
Prime Minister George Papandreou has offered to step down in favour of a coalition government.
But the leader of the main conservative opposition party, Antonis Samaras, has called instead for immediate elections.
President Carolos Papoulias is holding meetings on Sunday to try and get the political parties working together.
The Opposition leader was due to hold talks with President Papoulias on Sunday morning before Mr Papandreou convenes an emergency cabinet meeting in the afternoon.
Eurozone finance ministers will meet this week to debate an eight billion euro slice of bailout cash that the Greek finance minister says is needed by 15 December.
"The application of this deal is the precondition for us staying in the euro - it's as important as that," Mr Papandreou told reporters on Saturday after visiting President Papoulias.
Mr Papandreou was referring to a rescue package thrashed out in late October after tortuous negotiations in Brussels that would see banks write off half their holdings of Greek debt and offer massive loans to keep the country afloat.