Alexis Tsipras, the Greek prime minister, asked to meet Jean-Claude Juncker on Saturday but was spurned by the European Commission president rankled by the Greek leader's denunciation of his efforts to broker a bailout deal.
Mr Tsipras met with Mr Juncker in Brussels on Wednesday to discuss a compromise agreement hammered out by the European Commission chief and the leaders of Greece's other two creditors, the International Monetary Fund and the European Central Bank.
At the time, Mr Tsipras said "progress was made" at the Brussels meeting with Mr Juncker. But in a fiery speech before the Greek parliament Friday night, Mr Tsipras lashed out, saying he was "unpleasantly surprised" by the offer made by Mr Juncker, calling the proposals "absurd" and "irrational, blackmailing demands".
"I would like to believe that this proposal was an unfortunate moment for Europe, or at least a bad negotiating trick, and will very soon be withdrawn by the same people who thought it up," Mr Tsipras told the Greek parliament.
According to a senior official with a Group of Seven delegation, which began gathering in southern Germany on Saturday ahead of a two-day summit of the leaders of the seven leading industrialised powers that begins Sunday, Mr Juncker believed Mr Tsipras' speech in parliament left little to discuss.
"Unless he seriously addresses the issues, there's no reason to meet," said the G7 official.
A senior Greek official, however, denied that Mr Tsipras had requested a meeting with Mr Juncker. The official said Greece's differences now lie with Berlin, not Mr Juncker in Brussels.
The G7 official said Greece's creditors were taken by surprise both by Mr Tsipras' outright dismissal of their offer in his parliamentary address as well as a decision to delay a 300 million euro loan repayment owed to the IMF last Friday.
Although IMF rules permit Greece to bundle the four payments totalling 1.5 billion euro it owes in June and pay at the end of the month, the rule has not been invoked since Zambia in the 1980s, and EU officials left Wednesday's meeting believing Athens would make the payment.
Mr Juncker and Mr Tsipras, along with Jeroen Dijsselbloem, the Dutch finance minister who heads the committee of his 18 eurozone counterparts, were due to meet again in Brussels on Friday. But the meeting was postponed after Mr Tsipras decided he needed to address the Greek parliament to stem growing outrage about the creditors' offer from within his own ruling Syriza party.
Mr Juncker's rejection of a meeting with Mr Tsipras returns the bailout talks to a point of stalemate just a week after creditors believed the talks were making progress for the first time in nearly four months.
Despite the snub from Mr Juncker, eurozone officials said Mr Tsipras had one of his regular phone calls with Angela Merkel, the German chancellor, and Francois Hollande, the French president, on Saturday. Officials characterised the call as constructive.
Many officials believe a deal to release 7.2 billion euro in desperately-needed bailout aid needs to be reached ahead of a June 18 meeting of eurozone finance ministers so that Athens has enough time to implement an agreed set of economic reforms in order to get the rescue funds before the bailout expires at the end of the month.
Without the 7.2 billion euro in aid, Greece is expected to default on the 1.5 billion euro IMF bill as well as two large sovereign bonds held by the ECB which come due in July and August totaling 6.7 billion euro.
The European Commission, and particularly Mr Juncker, have long seen themselves as Greece's strongest advocate at the creditors' table, frequently clashing with the more hardline views of the IMF and the German finance ministry.
Mr Tsipras' speech Friday was the second time his government has publicly spurned Commission efforts, however. In February, Yanis Varoufakis, the charismatic Greek finance minister, publicly revealed Pierre Moscovici, Mr Juncker's economic commissioner, had been quietly attempting to broker a compromise deal to extend Greece's bailout without Mr Dijsselbloem's knowledge.
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