EU leaders were headed into a summit in Brussels on Thursday with no clear resolution to a standoff over debt and austerity between Greek officials and international lenders that could force the country out of the eurozone.

"The decision lies exclusively with the Greek authorities," German Finance Minister Wolfgang Schäuble said on his arrival. "They have, however, rather gone backwards."

Germans have largely supported their government's calls for Greece to introduce further austerity measures, with the health of the euro often cited as a prime concern. Earlier this week, Greek Finance Minister Yanis Varoufakis (pictured) said German Chancellor Angela Merkel faced a "stark choice".

Greece needs international loans to pay 1.6 billion euros ($1.8 billion) to the International Monetary Fund by the end of June. A default, which could occur by Tuesday, could bankrupt the country, destabilize markets and damage the European Union.

'Rift, Greece's humiliation'

Greece's economy collapsed in 2009 as part of the global financial meltdown, and the damage deepened with news that a previous, right-wing government had hid massive debts for years, forcing the country to take two loans totaling 240 billion euros since 2010. In January, Greeks chose Syriza to put a stop to years of crippling austerity imposed from abroad as a condition of the credit line.

Among other issues, Greeks and international institutions differ on pensions, taxation, labor law and public wages. With the country tapped out after years of cutbacks, Prime Minister Alexis Tsipras faces immense pressure not to backtrack on election promises. However, a default could trigger a bank run - an estimated 4 billion euros were moved out of accounts last week alone - and capital controls, setting Greece on an uncharted path out of the 19-nation eurozone.

"The lenders' hard-core faction does not want a deal but a rift, Greece's humiliation and the fall of the Tsipras government," tweeted Dimitrios Papadimoulis, a Syriza member of the European Parliament.

Eurozone finance ministers would have to approve any deal, followed by the leaders of EU member states. The deal would have to be endorsed in Greece's parliament, as well as by majority votes in EU member legislatures. In Germany, lawmakers were reportedly told to prepare for a session next Tuesday.

"Work is under way, and it can still take many hours," European Council President Donald Tusk said Thursday, arriving at the EU summit in Brussels. "But I have a hunch that, unlike in Sophocles' tragedies, this story will have a happy end," he added in an odd reference to a 2,500-year-old Greek playwright.

mkg/jil (Reuters, AFP, dpa, AP)