A.M. Best Co. has affirmed the financial strength ratings of A++ (Superior) of Sun Life Assurance Co. of Canada and its core subsidiaries, Sun Life Assurance Co. of Canada (U.S.), and Sun Life Insurance and Annuity Co. of New York.

Concurrently, A.M. Best has affirmed all of Sun Life’s existing debt ratings. A.M. Best has also affirmed the financial strength rating of A+ (Superior) of Keyport Life Insurance Co. All rating outlooks have been changed to negative from stable.

In a statement released Thursday, A.M. Best said the ratings reflect Sun Life’s diversified and profitable operations, solid capitalization and very strong market position in Canada.

The ratings agency added that Sun Life’s earnings are supported by its diverse operations, which are anchored by its very strong franchise in the Canadian market and complemented by its prominent position in the U.S. fixed annuity business. It noted that Sun Life is also well-positioned for significant growth in Asia.

The ratings agency said that these strengths are tempered by the highly competitive and consolidating nature of the Canadian market, which A.M. Best believes will make it increasingly difficult for Sun Life to grow market share.

It said that should Sun Life pursue acquisitions, its financial leverage may increase beyond A.M. Best’s expectations for the current rating level. Accordingly, the rating outlook is negative.

For a comprehensive list of Sun Life’s financial strength and debt ratings, please visit www.ambest.com/press/090404sunlife.pdf.