Speaking at the Group of Seven (G-7) summit in Germany on Sunday, Juncker said he was a "little bit disappointed by the speech."
"He was presenting the offer of the three institutions (to the Greek parliament) as a 'take-it-or-leave-it-offer'. That was not the case. That was not the message given to him. He was presenting the offer of the three institutions as being mine and mine exclusively. He knows perfectly well that this is not the case. And he knows perfectly well that I was - during the meeting we had last Wednesday- perfectly ready to discuss on the main points where disagreements are between Greece and the three institutions."
"As I told you before, I am waiting for an alternative proposal of our Greek counterparts. I do not have a personal problem with Alexis Tsipras, quite the contrary. He was my friend, he is my friend. But friendship - in order to maintain - it has to observe some minimal rules," Juncker said.
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It was also reported that Juncker refused a request from Tsipras to meet him on Saturday, feeling that the speech on Friday left little to discuss, Reuters reported.
Negotiations between Greece and its international creditors over a reforms-for-aid deal are expected to continue this week and, after four months of inconclusive talks, it's no wonder that tempers are getting frayed.
Greece owes billions of euros worth of debt repayments over the summer and chose last week to bundle its four payments due to the International Monetary Fund (IMF) into one lump payment to be paid at the end of the month.
Whether Athens and its creditors can continue to delay reaching an agreement is a matter for debate, however, with expectations rising that Greece could default on its debt and potentially leave the euro zone altogether.
According to a poll by Swiss asset management group GAM of 78 institutional investors just over a third of those surveyed believe Greece will leave the euro zone before the end of May next year.
Christian Noyer, a member of the ECB's Governing Council, said on Monday that it would not be problematic for the currency union if Greece quit, according to Reuters.
He added that Greece had only "a matter of days" to reach a deal, the news service reported.