In the strongest language since the start of the six-month stand-off between the far-left government in Athens and eurozone lenders, EU leaders said the No vote in last Sunday’s referendum had severely constrained their ability to offer Greece aid and warned any new bailout deal would include much tougher terms than those that could have been reached just two weeks ago.

“I am strongly against Grexit but I can’t prevent it unless the Greek government do what they need to do,” said Jean-Claude Juncker, the European Commission president. “We have a Grexit scenario prepared in detail; we have a scenario as far as humanitarian aid is concerned.”

The decision to invite all 28 countries to Brussels to deal with the Greek crisis is unprecedented; since Greece first applied for a bailout five years ago, such euro-related summits have only been attended by heads of governments in the common currency.

Earlier on Tuesday, Greek negotiators had stunned eurozone finance ministers by arriving at their meeting without a revised economic reform proposal.