All updates in Universal Coordinated Time (UTC)

16:10 Greek Defense Minister Panos Kammenos, who is also the leader of the right-wing junior partner in the Syriza-led coalition, said Athens' reform proposals "will be submitted shortly."

15:46 Europe's main stock markets closed higher on hopes that a Greek debt deal was imminent. Frankfurt's DAX 30 ended trading up by 2.32 percent and the CAC 40 in Paris was even better, posting a gain of 2.55 percent. London's benchmark FTSE 100 gained 1.4 percent on the day.

14:32 German Finance Minister Wolfgang Schäuble said the possibility of some kind of debt relief would be discussed over the next few days, but that this could not include an outright debt cut.

"The European treaties rule out a debt cut," Schäuble said.

13:55 German Finance Minister Wolfgang Schäuble said at the Bundesbank conference in Frankfurt that his new Greek counterpart, Euklid Tsakalotos, needed to take swift, concrete action to help rebuild trust with Athens' eurozone partners.

"Go into your parliament and just do it," Schäuble said.

At the same time though, he conceded that the chance of Greece implementing such action before Sunday's European summit was "rather limited."

13:31 Olivier Blanchard - director of research at the International Monetary Fund (IMF) - said that the world economy "withstood the stress tests of the last two weeks fairly well," referring to Greek Prime Minister Alexis Tsipras' decision to call a referendum, which promptly ended negotiations between Greece and its creditors.

"We continue to hope for and work toward a positive solution which Greece remains in the eurozone," he said.

"There is little question that Greece is suffering and may suffer even more under the scenario of a disorderly exit from the eurozone. But the effects on the rest of the world economy are likely to be limited," Blanchard said.

13:04 The IMF said the eurozone was experiencing a "robust recovery," adding that developments in Greece have "not resulted in any significant contagion."

"The economic recovery in the euro area seems broadly on track, with a generally robust recovery in domestic demand and inflation beginning to increase," the IMF said in an update to its World Economic Outlook report.

"Growth projections have been revised upward for many euro area economies, but in Greece, unfolding developments are likely to take a much heavier toll on activity relative to earlier expectations," the report added.

12:09 European stock markets reacted positively after President of the European Council Donald Tusk announced that Greece's debt burden will be discussed at Sunday's EU summit. The Stoxx 50 index - comprising Europe's leading shares - was up 2.6 percent following Tusk's statement.

10:57 Sunday's Euro summit is scheduled to start at 14:00 with a special meeting of the European Council to follow.

10:19 Tusk said that he hopes to receive "concrete, realistic reform proposal today" after speaking with Greek Prime Minister Alexis Tsipras.

"Realistic proposal from Athens needs to be matched by realistic proposal from creditors on debt sustainability to create win-win situation," Tusk said in a message on Twitter.

09:37 Tsipras is meeting with Finance Ministry officials amid Thursday's looming deadline. The Greek government is rushing to put together the final details of a proposal that is expected to see pension and tax reforms.

09:25 President of Germany's central bank Jens Weidmann said that the Governing Council of the European Central Bank (ECB) - which he is a member of - should not continue to provide Greek banks with Emergency Liquidity Assistance (ELA). On Wednesday, the ECB decided to continue its ELA lifeline to Greek banks.

"It needs to be crystal-clear that responsibility for further developments in Greece and for any decisions on transferring financial resources lies with the Greek government and the countries providing assistance - not the ECB's Governing Council," Weidmann said.

The Bundesbank chief's statement comes amid Athens' decision to keep Greek banks closed until next Monday.

09:00 IMF chief Christine Lagarde said on Wednesday that a new plan to move forward in the Greek crisis would require debt restructuring.

"The other leg is debt restructuring, which we believe is needed in the case of Greece for it to have sustainability," she said.

More to follow.

ls,pfd/jil (AFP, AP, Reuters, dpa)