Greece's European partners shut the door on extending a credit lifeline to Athens, leaving it facing a default that could push it out of the euro after the leftist government rejected tough lender demands and put their bailout deal to a referendum.
Finance ministers of the other 18 countries sharing the euro met for the first time without Greece and flatly rejected its pleas to extend an expiring bailout until after the referendum on 5 July and setting the stage for Athens to default on a crucial IMF payment on Tuesday.
The 18 pledged to do whatever it takes to stabilize the common currency area and said they were in much better shape to do so than at the height of the eurozone crisis a few years ago.
In a formal statement, they also implicitly urged Greece to impose capital controls to stabilize its banking system.
The rejection of an extension piled huge pressure on Greek banks, which depend on central bank support to remain afloat, with long lines forming in front of cash machines as people rushed to pull their money out while the banks were still operating normally.
After its surprise decision to call a referendum on the bailout, Athens asked for an extension of Greece's bailout programme beyond Tuesday, the day it must pay €1.6 billion to the International Monetary Fund or default.
But the other 18 members of the euro zone unanimously rejected the request, freezing Greece out of further discussions with the European Central Bank and the IMF on how to deal with the fallout from a historic breach in the EU's 16-year-old currency.
The swift rejection was a startling demonstration of the degree to which Mr Tsipras had alienated the rest of the currency bloc with a final-hour announcement that upended five months of intense talks.
The Eurogroup of finance ministers shut Greece's Yanis Varoufakis from a meeting in Brussels and issued a statement without him, accusing Athens of breaking off negotiations unilaterally.
"The current financial assistance arrangement with Greece will expire on 30 June, 2015, as well as all agreements related to the current Greek programme," it said, making clear its refusal of a grace period to hold the vote.
Mr Varoufakis said the refusal to provide an extension "will certainly damage the credibility of the Eurogroup as a democratic union of partner member states".
"I'm very much afraid that that damage will be permanent."
The Greek parliament met to approve the referendum, with pro-European opposition parties uniting in condemning the decision and fuelling speculation that Mr Tsipras' left wing government may have to resign if voters back the bailout in the 5 July referendum.
Greek President Prokopis Pavlopoulos was expected to meet former conservative Prime Minister Antonis Samaras on Sunday.
The offer from creditors requires Greece to cut pensions and raise taxes in ways that Mr Tsipras has long argued would deepen one of the worst economic crises of modern times in a country where a quarter of the workforce is already unemployed.
Caught between fears of economic collapse and defiance of the demands from international creditors, many Greeks expressed shock, although opinion polls published in Sunday newspapers pointed to a majority in favour of accepting the bailout terms.
However voters in other euro zone states -- including the bloc's economic powerhouse Germany, other southern states which have suffered austerity in return for EU cash and poor eastern countries with living standards much lower than Greece – have lost patience.
Solution to Greek debt still possible - Michael Noonan
Finance Minister Michael Noonan has indicated it may still be possible to reach a deal between Greece and its creditors.
Minister Noonan said there is still time to cut a deal.
He said he did not have any fears over the euro as, he said, the currency was in a very strong position.
He said he has sympathy for the Greek people and said he would like to see progress made, "even at this late stage."
When asked if he thought Greece should hold a referendum as planned on the bailout deal, Minister Noonan said that was a matter for the Greeks to decide.
'Greece should remain in the euro despite difficulties' - Michel Sapin
Many questions remained over the referendum, which is being called over the terms of a bailout offer that may no longer be on the table.
But with fears growing that the foundations of the eurozone could be fatally weakened if Greece were forced out, French Finance Minister Michel Sapin insisted that Paris, at least, was still prepared to talk.
"The 18 countries, apart from Greece, all said clearly that Greece was in the euro and should remain in the euro whatever the difficulties of the moment," he said.
Although European officials have repeatedly insisted that financial firewalls built during the eurozone debt crisis of the past six years would limit the impact of any "Grexit", the longer-term effects are completely unknown.
Jeroen Dijsselbloem, the Dutch finance minister and chair of the Eurogroup, said Greek lawmakers should think about whether the referendum was wise before agreeing to hold it, essentially appealing directly to the Greek parliament to defy Mr Tsipras when it votes on approving the measure later today.
Underlining the mutual incomprehension that has marked months of often angry exchanges between the Syriza government and its European partners, Finance Minister Yanis Varoufakis was still holding out hopes of a deal.
"In these crucial moments, the Greek government is fighting for there to be a last-minute deal by Tuesday," he said after the euro zone had rejected further talks and said it would cutoff financial support from 30 June.
He added the government would be prepared to recommend that voters backed the deal if lenders agreed to improve the terms.