The eurozone has given Greece until Thursday to present new proposals to secure a deal with creditors, and has called a full EU summit for Sunday.
European Council President Donald Tusk said this was now the "most critical moment in the history of the eurozone".
The eurozone had expected Greece to submit fresh plans on Tuesday after its voters rejected a deal in a referendum, but no new proposals were tabled.
On Sunday, a meeting of all 28 members of the European Union will be held.
Read more: Greece debt crisis: Eurozone sets deadline for new plan - BBC News