Fitch credit rating agency further downgraded Greece's credit worthiness on Wednesday, according to the Greek national broadcaster NET, DPA reported.
The long-term credit rating dropped from "B-" to "CCC".
There was no immediate reaction from the Finance Ministry in Athens.
In a statement, Fitch said the rating downgrade "reflects the absence of a new, fully-funded and credible EU-IMF programme for Greece, coupled with heightened uncertainty surrounding the role of private creditors in any future funding, as well as Greece's weakening macroeconomic outlook."
It said any new programme of funding bailouts would only be credible if they extended beyond mid-2013.
It also said the privatization programme of Prime Minister George Papandreou looked "increasingly challenging."
The agency said its new "CCC" rating was a sign that "default is a real possibility."