AM Best Co has upgraded the issuer credit ratings (ICR) and senior debt ratings to “a” from “a-” for Ace Ltd and Ace INA Holdings Inc.Concurrently, Best has upgraded the ICR to “aa” from “aa-” and affirmed the financial strength rating of A+ (superior) of Ace Bermuda Insurance Ltd, Ace Tempest Reinsurance Ltd, Ace American Pool and its members, Ace INA Insurance (Canada).In addition, AM Best Europe - Rating Services Ltd has upgraded the ICR to “aa” from “aa-” and affirmed the FSR of A+ (superior) of Ace European Group Ltd (UK).Additionally, Best has upgraded the ICR to “aa” from “aa-” and affirmed the FSR of A+ (superior) of Ace Tempest Life Reinsurance Ltd (Bermuda). At the same time, Best has upgraded the ICR to “a+” from “a” and affirmed the FSR of A (excellent) of Combined Insurance Company of America (Glenview, Ilinois) and Combined Life Insurance Company of New York (Latham, New York).Best also has affirmed the FSR of A- (excellent) and ICR of “a-” of Ace Life Insurance Company (Ace Life) (Stamford, CT). The outlook for all ICRs has been revised to stable from positive, while the outlook for all FSRs is stable, except for the outlook for Ace Life, which is stable for both ratings.In addition, the ratings agency has affirmed the FSR of B- (Fair) and ICR of “bb-” of Century Indemnity Company, the run-off entity of Ace. The outlook for these ratings is stable. Concurrently, Best has withdrawn these ratings at the company’s request. All companies are domiciled in Philadelphia.