Moody's has put the financial strength ratings of Ace primary US operations under review for a possible downgrade.
The agency has also changed the ratings outlook to negative from stable.
The move was taken following the company's announcement yesterday that it would record a $298m after-tax charge associated with the completion of its asbestos and environmental review.
At the same time, Moody's placed the A2 insurance financial strength ratings of the Ace American pool companies and the Ba3 financial strength ratings of Century Indemnity Company and Century Reinsurance Company under review for possible downgrade.
The Ba3 financial strength rating for Ace American Reinsurance Company has been placed on review with direction uncertain.
Moody's said the move was due to Ace's plans to sell off two run-off reinsurance companies to Randall & Quilter Investment Holdings.