Ratings agency A.M. Best Co. has placed the financial strength rating of A+ (Superior) and the issuer credit ratings of “aa” of Swiss Reinsurance Co. and its similarly rated subsidiaries under review with negative implications.

Concurrently A.M. Best has placed all debt issued or guaranteed by Swiss Re under review with negative implications.

These rating actions follow Swiss Re’s announcement of a CHF 1.2 billion (US$1.1 billion) mark-to-market loss, or CHF 981 million (US$890 million) after tax, arising from its exposure to two credit default swaps written by its credit solutions unit. The loss has resulted from the unprecedented ratings downgrades in October and the lack of liquid markets for the underlying securities.

A.M. Best says it will discuss with Swiss Re’s management the potential for further write-downs arising from this exposure.

In addition, although the loss does not exceed Swiss Re’s credit risk tolerance, A.M. Best says it will further evaluate Swiss Re’s enterprise risk management in light of this unexpected loss and the steps Swiss Re has taken to minimize such financial risks in the future.

For a complete listing of Swiss Re’s ratings, please visit www.ambest.com/press/112003swissre.pdf.