ATHENS, Greece — Anxiety over Greece's future swelled on Saturday, with people queuing outside banks to withdraw cash, after Prime Minister Alexis Tsipras' call for the people to vote on a proposed bailout deal increased the risks that the country might fall out of the euro.

The call for a vote has strained relations to a near breaking point between Greece and its creditors, some of which say there may be little left to do to save Greece after five months of fruitless and frustrating talks. The sides are haggling over the reforms the country needs to make in exchange for more financial aid but have managed to only increase uncertainty over the country's future.

Greece has a debt due on Tuesday and its bailout program expires the same day, after which it is unclear whether its banks would be able to avoid collapse, an event that could be the precursor to Greece leaving the euro.

The Greek Parliament is debating and will vote at midnight Saturday on the government's request for a referendum, as finance ministers from the 19 euro countries, Greece's main creditors, gathered to discuss the situation in Brussels.

Across Athens, people started flocking to cash machines shortly after Tsipras announced the referendum around 1 a.m. local time. The queues grew the next day, though the number of people and the availability of cash varied widely. The Bank of Greece assured in a statement Saturday that the flow of cash will not be interrupted.

The concern over what awaits the country in the hours and days to come was palpable. At one branch of Pireaus Bank in central Athens, one of very few that opens on Saturdays, about 50 people queued up in the early morning before they found out the bank would not open at all. An elderly woman fainted.

The referendum will ask Greeks to vote on a proposal of reforms that the country's creditors made on Thursday. The Greek government rejected it as imposing cuts that are too harsh on the general population.

The Greek government said it would recommend Greeks vote "no" in the referendum. What would happen in that case — whether Greece would have to leave the euro or try to renegotiate more time with creditors — is unclear.

Eurozone officials were openly frustrated by the Greek move and increasingly pessimistic.

"I am very disappointed," said Jeroen Dijsselbloem, the Dutchman who leads the eurozone finance ministers' meetings. "After our last meeting, the door on our side was still open, but that door has closed on the Greek side."

Finland's finance minister, Alexander Stubb, said the eurozone should now discuss a Greek exit from the single currency: "I think that's the only option we have to discuss because there's nothing else on the table."

If it became accepted among European politicians that Greece could not agree on a rescue deal, the European Central Bank could decide to end the emergency credit that it allows Greek banks to draw on. The banks would likely collapse and the Greek government would have to support them itself. Penniless, the government would have to revert to printing a new currency, effectively drawing the country out of the euro union.

Such a move would put the country through a new era of economic pain. With the new currency less valuable than the euro, the government would have to write off a chunk of its foreign loans — mainly owed to eurozone countries — and many companies and households would go bankrupt. Experts predict a long and deep recession in a country that has already been through five years economic depression.

The uncertainties of all this would roil European and global markets, though experts are divided on the extent. Some say Europe is better equipped to handle a Greek euro exit, but others say it is unclear what might happen. The euro dropped in value slightly on international markets after the referendum was called.

As the country came to grips with what lay ahead, former prime minister Costas Karamanlis broke a longstanding silence and criticized the government.

"The nation's most vital interests demand that the country remains at the heart of Europe. The EU's actual shortcomings do not, in any way, negate this..." Karamanlis said. "Foolish choices that undermine this principle push the country to adventures, with unpredictable and possibly irreversible consequences."

Panagiotis Lafazanis, a senior Syriza minister overseeing the energy sector, environment and agriculture, came out strongly against approving the creditors' proposal in a referendum.

"A 'No' will provide a big respite for Greece and the Greek people," he said in Athens. "It will be a big yes to a new era of reconstruction and progress." Asked if this would take place inside or outside the euro, he said "It is you (the media) who pose this dilemma. The dilemma for the people is whether they will live better."

Health Minister Panayiotis Kouroumblis, on the other hand, said that Greece does not want a rupture with Europe. "The referendum is part of the negotiation," he said.

In the streets of Athens, views were mixed on the merits of holding a referendum.

"The people are not in a position to decide. Those who are in position to decide are the ones that know a bit more and they must explain and simplify the issues for the people," said Grigoris Kanellopoulos, 41, a street seller of bagels.

Athina Kontosozou, 56, has already made up her made about how she will vote.

"No (to the creditors' proposals), no to any more measures. We don't know what will happen (after the referendum). Let's hope that things will be better. And they will get better. We believe it".


Thanassis Stavrakis and Paris Ayiomamitis in Athens, Greece, and Raf Casert, Derek Gatopoulos and Lorne Cook in Brussels contributed to this report.