BERLIN (AFP) - German Chancellor Angela Merkel said Tuesday she was not aware of any new EU debt deal proposal to Greece after European Commission chief Jean-Claude Juncker raised the prospect of a last-minute solution.

Asked about an 11th-hour offer to Athens, Merkel told reporters: "The only thing I know is that the last offer I am aware of is the one from last Friday. There is nothing more I can say."

Juncker revealed his surprise proposal just hours before Greece's bailout program expires at 2200 GMT with a huge debt repayment to the IMF also due Tuesday. Athens has confirmed it would not be able to make the deadline.

The deal would involve Greece accepting reform proposals that its EU-IMF creditors made at the weekend and backing a "yes" vote in a popular referendum on the deal on Sunday, Juncker's spokesman said in Brussels.

Merkel said she had no "credible indications" that Tuesday's deadline had shifted but she reiterated that the "door is open" to further talks with Athens.

"Of course we won't cut off the lines of communication after midnight -- we wouldn't be the European Union if we did that," she said, after a meeting with Kosovo's visiting Prime Minister Isa Mustafa.

"That means the door is open for talks but that is all I can say."

A German government source said earlier when asked about Juncker's initiative that it was "too late for a formal extension of the second aid program for Greece.”

Talks between Greece's leftist government and its creditors fell apart after Tsipras called the shock referendum on the latest EU proposals presented on Friday, which Athens has argued put too heavy a burden on the debt-mired country.