Eurozone finance ministers have rejected a Greek request to extend a bailout programme beyond 30 June.
Eurogroup head Jeroen Dijsselbloem said talks on a new bailout had been ongoing on Friday when Greece called a surprise referendum over the terms of any deal.
By doing so they broke off the process, he said.
Greece has to pay €1.6bn (£1.1bn) to the IMF on Tuesday. Without new funds, there are fears Greece may leave the euro and its economy may collapse.
Dijsselbloem said finance ministers would reconvene to discuss the consequences of the latest developments.
They were determined “to maintain the strength and credibility of the Eurozone”, he said.