A new opinion poll on Greece's bailout referendum pointed to a closely balanced result in the vote that could decide the country's future in Europe.
The poll, conducted by the ALCO polling institute and published in the Ethnos newspaper on Friday, reflected a sharp swing from a previous opinion poll that showed the No vote backed by the left-wing government strongly ahead.
The new poll gave a slight lead for the Yes vote in favour of the bailout at 44.8 percent against 43.4 percent for the No vote. 11.8 percent were undecided.
Previously, the only full survey to be released since the referendum was announced showed the "No" vote ahead, but falling sharply after the announcement that banks would be shut.
The latest poll was published a day after the International Monetary Fund delivered a stark warning of the huge financial hole facing Greece.
The IMF, part of the lenders' "troika" behind successive international bailouts, said Greece needed an extra 50 billion euros over the next three years, including 36 billion from its European partners, to stay afloat.
It also needed significant debt relief.
The assessment, in a preliminary draft of the IMF's latest debt sustainability report, underlines the scale of the problems facing Athens, whatever the result of Sunday's referendum on the bailout offered by creditors last month.
Prime Minister Alexis Tsipras' rejection of what he terms the "blackmail" of EU and IMF creditors demanding spending cuts and tax hikes has so angered Greece's partners that there is no hope of reconciliation before Sunday.
With banks closed for a fourth day on Thursday and capital controls in place, the future of the left-wing government hangs on the result, given the angry mood of voters in Greece, torn between resentment of the lenders and scorn for their own politicians.
On Sunday it will fall to the Greek people to decide an issue that their government was unable to settle in months of acrimonious negotiations with their European partners.
Consequences of a 'No'
"We are asking them to vote with their eyes open and think hard about all the consequences of a 'No' vote, which could lead Greece to leave the eurozone," French Prime Minister Manuel Valls said on the sidelines of an economic summit in Lyon.
The comment reflected the fear of many in the eurozone that a Greek exit would change the nature of a 15-year-old currency union intended to be unbreakable.
For Tsipras, if voters back a bailout plan that he has scorned, his government is likely to fall, leading to new elections by September.
Already, his coalition is crumbling as a succession of deputies from the right-wing Independent Greeks, his junior partners, have backed the 'Yes' vote.
Tsipras and his finance minister, Yanis Varoufakis, remain convinced Athens can negotiate better terms, including debt relief, if voters reject the conditions on offer. But both have signalled they will quit if voters choose the bailout.
"I want to believe that these problems won't last long," Tsipras said on Thursday of the bank closures. "The banks will open when there is a deal," he said in a television interview, predicting it would come within 48 hours of the referendum.
The IMF analysis suggested that, even on the most optimistic assumptions, the Greek economy would remain on life support for many years to come, and that Athens would be forced to persuade its European partners to help.
Loans made by Europe "will need to be extended significantly" and Greece would need further concessional financing, it said.
The ratings agency Standard & Poor's said Greece's economy, which has already shrunk 25 percent since 2009, would contract by another 20 percent within four years if it made a distressed exit from the euro.