The European Union faces "the most critical" moment in its 64-year history, after leaders warned they had five days to prevent Greece from careering out of the euro and into a full blown humanitarian crisis.

"Our inability to find agreement may lead to the bankruptcy of Greece and the insolvency of its banking system", said Donald Tusk, head of the European Council, after talks between Greece and its partners ended without agreement on Tuesday night.

• Greece crisis live

Brussels has now convened a full emergency summit of all 28 European leaders on Sunday to thrash out an deal to keep Greece in the single currency.