The troubled institution cannot access capital markets, and in July announced plans to sell itself.
But its long-term future is far from assured and the state could end up becoming involved, said Moody’s, due to the “rising probability” that 3CIF will not be able to roll-over at least €1.75bn (£1.39bn) in maturing debts in October.
Previously the credit rating included a 12-notch boost from the lender’s implicit state backing – a level of support that Moody’s has now cut to nine points.
That is because any government intervention “could potentially be less favourable for creditors than an acquisition by a strong strategic partner”, the agency warned.
Meanwhile Moody’s put New York state-based M&T Bank on review for a downgrade after it announced plans to snap up Hudson City Bancorp in a deal worth roughly $3.7bn (£2.34bn).
The agency will study Hudson’s credit profile and “the integration challenges it presents”, in part because this is M&T’s largest ever acquisition.