During the three-and-a-half hour call Juncker said the ministers of the 17 eurozone countries had received assurances from Greece that it had found a further 325 million euros (£270 million) in cuts on top of austerity measures already agreed.
Greek coalition leaders also gave "strong assurances," from the leaders of the two Greek parties that make up the coalition government to implement promised cuts and reforms even after elections expected in April.
The Eurogroup had been due to meet in Brussels but a face-to-face meeting to discuss the 130-billion-euro (£108 billion) package on Wednesday was cancelled after Athens failed to provide sufficient commitments on austerity and ensure that paperwork was complete. A decision on a second bailout program for Greece was postponed until Monday.
The second bailout program comes after an earlier 110 billion-euro-scheme agreed between Greece and its creditors in May 2010. The eurozone wants Greece to dramatically reduce its debt burden from 160 percent of gross domestic product to 120 percent by 2020.
Meanwhile the clock is ticking for Greece to secure the second bailout because technical procedures to avoid a 14.5-billion-euro default on March 20 are expected to take several weeks. Greek Finance Minister Evangelos Venizelos has warned that the country's future as a member of the eurozone is on a "knife's edge."
Tensions had been running high ahead of the conference call after German Finance Minister Wolfgang Schäuble told German public radio that efforts to help Greece did have their limits.
"We want to do everything we can to help Greece," said Schäuble. "We can help but we are not going to pour money into a bottomless pit."
The reference to a bottomless pit prompted an angry response in Greece, not least from President Carolos Papoulias.
"I do not accept having my country taunted by Mr Schäuble, as a Greek I do not accept it," said Papoulias, who also blasted the Netherlands and Finland for their tough stance.
"Who is Mr Schäuble to taunt Greece? Who are the Dutch? Who are the Finns?" asked Papoulias.
In the European Parliament in Strasbourg, Italian Prime Minister Mario Monti warned against a breakup of the eurozone but also claimed that Greece had brought its problems upon itself.
"Let's not forget that the policies conducted in Greece over several years were a perfect catalogue of the worst practices in Europe," he said.
Greece is now in its sixth year of recession, with unemployment at more than 20%; youth unemployment is close to 50% and climbing.