Prime Minister Alexis Tsipras announced a referendum set for July 5 to determine the country's next steps should an agreement be reached at the latest make-or-break meeting in Greece's standoff with international creditors.
Tsipras said Greece wanted to remain part of the European Union, but that it also needed to send a message to the world.
The creditors are withholding the payout of the next 7.2 billion euros ($8.1 billion) in Greece's emergency loan package. Greece needs to make a 1.6-billion-euro repayment to the International Monetary Fund by June 30.
The IMF, Germany and co-creditors have called for Greece to continue introducing new austerity measures after years of a shrinking economy.
"These proposals - which clearly violate the European rules and the basic rights to work, equality and dignity - show that the purpose of some of the partners and institutions was not a viable agreement for all parties, but possibly the humiliation of an entire people," Tsipras said of years of enforced austerity.
Late Friday, Finance Minister Yanis Varoufakis told Greek television that the two sides needed to overcome their differences when he met his counterparts on Saturday: "There is no reason why there should not be an agreement at the Eurogroup tomorrow. We have a duty to find a solution."
Earlier, however, Varoufakis had called the latest offer by creditors "clearly unviable."
Saturday's meeting of finance ministers in Brussels follows discussions involving government leaders at an EU summit that wrapped up on Friday. Tsipras met with both German Chancellor Angela Merkel and French President Francois Hollande on the fringes of the summit, which was also held in Brussels.
Without the last tranche of its bailout, not only could Greece go into default, but it could trigger a "Grexit," in which the country would lose the euro currency.
mkg/bk (Reuters, AFP, dpa, AP)