Eurozone leaders set Greece brutal take-it-or-leave-it conditions for a desperately needed bailout deal at a summit on Sunday as an exit from the single currency loomed ever larger.

Hawkish Germany pushed for a Greek "time out" from the euro if leftist Prime Minister Alexis Tsipras fails to agree terms for a three-year rescue plan worth up to 86 billion euros ($96 billion).

Russia is considering direct deliveries of fuel to Greece to help prop up its economy, Energy Minister Alexander Novak said Sunday, quoted by Russian news agencies.

"Russia intends to support the revival of Greece's economy by broadening cooperation in the energy sector," Novak told journalists, quoted by RIA Novosti news agency.

The EU canceled a full 28-nation summit on Sunday to decide Greece's fate in the single European currency, although a meeting of leaders from the 19 countries in the eurozone will go ahead as planned.

The announcement by European Council President Donald Tusk came as eurozone finance ministers met for a second day to continue "difficult" Greek bailout talks, with the aim of reaching a deal that eurozone leaders can sign off on.

Iran should boost trade with its Gulf Arab neighbors if a deal on its nuclear program sees sanctions and an oil embargo lifted, but higher Iranian crude production could worsen tensions within OPEC, analysts say.

As of Saturday, the prospects of such a deal were still very much in question, with no sign of an end to a nail-biting deadlock after 15 straight days of negotiations in Vienna between Iran and major world powers.

Indonesia is seeking to rejoin OPEC to get access to cheaper oil supplies as demand soars and domestic production falls, but critics say the move is an unwelcome distraction from efforts to overhaul the country's troubled energy sector. 

Resource-rich Indonesia, Southeast Asia's largest economy, was part of the Organization of the Petroleum Exporting Countries (OPEC) for almost 50 years until suspending its membership in 2009 after becoming a net oil importer.

Greece's eurozone partners were doubtful of a last-ditch bailout deal on Saturday, saying talks to stop it crashing out of the euro would be tough because trust in Athens had collapsed.

Hardline German Finance Minister Wolfgang Schaeuble led a chorus of skepticism about Greek Prime Minister Alexis Tsipras's new reform plan aimed at a third debt rescue package worth more than 80 billion euros ($89 billion).

An accounting scandal involving massive Japanese conglomerate Toshiba deepened on Saturday as reports said the company's president would likely be forced to resign.

The resignation of Toshiba President Hisao Tanaka will be finalized after a third-party panel tasked with investigating the scandal releases its report as early as next week, the Kyodo news agency said, citing unnamed sources.

Prime Minister David Cameron is seeking a British exemption from European Union employment laws as part of his push to gain more autonomy from Brussels, newspapers said Saturday.

The Conservative leader wants to restore opt-outs on EU legislation that were given up by Labor prime minister Tony Blair, who led the country from 1997-2007, both The Times and The Daily Telegraph reported, citing unnamed sources.

Fresh Greek bailout reform proposals were cheered by France and Italy on Friday, raising hopes that a last-ditch compromise could be reached with the country's creditors to prevent a dreaded "Grexit."

The plan delivered by Prime Minister Alexis Tsipras' administration for study by the EU, IMF and European Central Bank was to be put to a vote late Friday by Greek lawmakers.

The International Energy Agency forecast Friday that global oil demand growth would slow in 2016 and that oil production in nations outside the Organisation of the Petroleum Exporting Countries (OPEC) would stall.

In its first estimates for 2016, the IEA forecast that oil demand would slow next year to 1.2 million barrels per day, compared with an average of 1.4 million barrels per day this year.