"We have spent the last two weeks discussing who will meet who, where, and in what configuration," said Jeroen Dijsselbloem, leader of the Eurozone finance ministers. "There is no further time to lose."
A frustrated reaction to the deal from voters and governing Syriza Party members reflects the mood of most Greeks, who are sick and tired of wallowing in financial crisis.
The announcement of a four month extension emboldened investors and temporarily eased fears of an impending Greek exit.
The eurozone's financial heads failed to reach an agreement to resolve the Greek debt crisis for the second time in less than a week during negotiations in Brussels.
The new Syriza government in Athens hopes its international creditors will compromise over its debt program, but finance ministers say agreement is a long way off.
While a Eurogroup meeting in Brussels broke down without an agreement, people gathered peacefully in Athens to support their government's anti-austerity plan.
Greek Prime Minister Alexis Tsipras has made it clear that he won't back down from reversing austerity measures, raising the possibility of a new Eurozone crisis.
Supporters say the anti-austerity economist is the right man for the job in times of crisis. Critics accuse him of wanting to bankrupt the country, and take it out of the Eurozone.
Four decades of dominance over Greece by two major political parties is expected to end Sunday with a victory by Alexis Tsipras and his left-wing Syriza party, which will likely reject austerity measures imposed by international groups.