Standard & Poor's Ratings Services on Tuesday said it lowered its long-term counterparty credit ratings on Barclays Bank PLC, Credit Suisse AG (MLPN.P) and Deutsche Bank AG (DBKGn.DE) to A from A-plus.
S&P also affirmed the A/A-1 long-, and short-term ratings of UBS AG UBSN.VX.
The outlooks on all these banks are stable.
The rating actions are based on the "increasing risks that Europe's large banking groups active in investment banking face as regulators and uncertain market conditions continue to make operating in the industry more difficult," S&P said.
S&P will hold a live online discussion and webcast on these actions on July 3 at 9 a.m. EDT, 2 p.m. BST, 3 p.m. CEST.
(Reporting by Pam Niimi)