Supporters of Greece's bailout terms have taken a wafer-thin lead over the "No" vote backed by the leftist government, hours before a referendum that may determine the country's future in the euro zone, a poll showed.
The opinion poll by the respected ALCO institute, published in the Ethnos newspaper on Friday, put the "Yes" camp on 44.8 percent against 43.4 percent for the No" vote. But the lead was within the pollster's 3.1 percentage point margin of error, with 11.8 percent saying they are still undecided.
With banks shuttered all week, cash withdrawals rationed and commerce seizing up, the vote could decide whether Greece gets another last-ditch financial rescue in exchange for more harsh austerity measures or plunges deeper into economic crisis.
It could also determine whether Greece becomes the first country to crash out of the 19-nation European single currency area, membership of which is meant to be irrevocable.
The survey found that 74 percent of Greeks want to stay in the euro, while just 15 percent want to return to a national currency, with 11 percent undecided.
Prime Minister Alexis Tsipras has urged Greeks to reject the "humiliating" terms offered last week by international creditors in a deal that is no longer on the table, and accused lenders of "blackmail" by withholding credit.
As discontent has mounted over long queues for pensions and at cash machines, Tsipras promised voters that banks would reopen as soon as the government clinched a fresh loan from its euro zone partners.
Credit ratings agency Fitch said the banks were already effectively bust and would go to the wall within days unless the European Central Bank increases emergency liquidity assistance to help them cope with a wave of withdrawals.
There has been little time for campaigning but Tsipras is due to address a mass rally of "No" supporters in Athens' central Syntagma Square outside parliament on Friday evening, while "Yes" campaigners plan a rally at the old Olympic Stadium.
The "No" campaign has directed much of its venom at Germany, the euro zone's dominant power and Greece's biggest creditor.
One poster plastered in central Greece shows a picture of German Finance Minister Wolfgang Schaeuble with the slogan: "For five years he's been sucking your blood. Tell him NO now."
The Council of State, Greece's highest administrative court, is to decide on the constitutionality of the referendum at a hearing on Friday. The Council of Europe, a pan-European democracy and human rights watchdog, has said the vote does not meet its minimum standards.
Two Greek citizens are seeking the suspension of the vote as unconstitutional and illegal, arguing that it was called at too short notice, that the constitution bars questions relating to fiscal policy, and that the question is unclear and too complex.
Many Greeks may be unable to cast ballots, either because they are abroad and have to return to the country to vote, or because they do not have the money to return to their home constituencies because of the cash restrictions.