Greece’s leaders have until Sunday to finalize a plan to pay back their creditors and begin the process of rescuing the country's economy from bankruptcy and extending a lifeline to the nation’s weakened banking sector. Greece offered no such plan at an emergency summit on Tuesday and by the meeting’s close, the patience of European Union leaders was wearing thin.

Greece now has to submit a proposal, latest by Thursday, which will outline how the country intends to resolve the crisis and, on Sunday, leaders of the European Union's member states will convene to finalize the way forward. Before that, in a teleconference scheduled for early Wednesday, Greece is expected to request a bailout from the European Stability Mechanism.

“Until now I have avoided talking about deadlines,” Donald Tusk, president of the European Council, said on Tuesday, as reported by the New York Times. “But tonight I have to say it loud and clear — the final deadline ends this week.”

Meanwhile, a July 20 payment deadline by which Greece must pay 3.5 billion euros ($3.8 billion) to the European Central Bank is rapidly approaching. Currently, the ECB also provides Greece with tens of billions of euros in emergency loans -- a critical source of funding that could be halted if Greece fails to reach an agreement with its creditors.

German Chancellor Angela Merkel has warned that a bailout will only be possible if Greece promises to make major economic reforms such as pension cuts and tax hikes. But on Sunday, Greek voters vehemently rejected those ideas in a referendum.

Greece’s Prime Minister Alexis Tsipras, of the nation’s far-left Syriza Party, was elected in January on a platform that opposed budget cuts and other austerity measures imposed by a previous bailout.

Those developments have led to speculation about whether Greece may instead choose to give up the euro and return to its own national currency, which would permit the National Bank of Greece to devise a way to relieve the country of its debt burden.

EU leaders also are prepared to cast a vote on Sunday to distribute humanitarian aid to Greece if no deal can be reached and the country is pitched into instability.