Juncker said there were now extensive plans on how to cope with Greece's exit from the eurozone, should Greek premier Alexis Tsipras fail to deliver a viable proposal.

The comments came after a meeting of eurozone leaders at which it had been expected that Tsipras would put forward fresh proposals for bailout deal. According to a joint statement of EU leaders, Tsipras must set out Athens' proposals for a reform agenda in detail by Thursday.

"We have a 'Grexit' scenario prepared in detail" warned Juncker, who insisted that, nonetheless, he wanted Athens to stay in the single currency.

Promise of swift and speedy response

Tsipras made it clear that the message - that time was of the essence - had been received and understood. The Greek premier has been buoyed by the weekend referendum "no" vote, in which his electorate backed his rejection of creditors most recent cash-for-reforms offer. However, the impatience of his fellow EU leaders has become increasingly palpable.

"The process will be swift, it will be speedy, it will begin in the next few hours with the aim of concluding until the end of the week at the latest," Tsipras said.

The referendum saw 61 percent of Greek voters reject the last set of demands for more austerity from the EU and IMF. Tsipras is due to address the European Parliament in Strasbourg on Wednesday, when it is thought he may set out further details of Greece's proposals that would stave off financial chaos, and a widely-feared exit from the eurozone.

Growing sense of impatience

European Union leaders from all 28 member states are to hold a decisive summit on the Greek debt crisis Sunday. Chancellor Angela Merkel said on Tuesday she hoped there would be enough reform proposals from Greece to make it possible for the German parliament to approve negotiations. Merkel said after the summit that Greece needed a debt program lasting "several years."

Merkel and French President Francois Hollande had on Monday said they expected Greece to come forward with concrete proposals on a way forward in the Tuesday meeting.

Italian Prime Minister Matteo Renzi said he believed a definitive deal would be possible on Sunday. "Tonight the decision is that we wait until Sunday for the new proposal to the European institutions by the Greek government," said Renzi.

EU President Donald Tusk said the final deadline to reach an agreement on a new bailout for Greece "ends this week."

"The Greek government will, on Thursday at the latest, set out in detail its proposals for a comprehensive and specific agenda," said Tusk. "Inability to find an agreement may lead to bankruptcy of Greece and insolvency of its banking system," he added.

Meanwhile on Tuesday, European Central Bank (ECB) chief Mario Draghi assured eurozone leaders that the ECB would do what is necessary to keep Greek banks afloat until the Sunday summit.

rc/jr (AFP, AP, dpa, Reuters)