AM Best has placed Sompo Japan Insurance Inc and its subsidiaries under review with “positive implications” after the group announced plans to buy Aspen Insurance Holdings Ltd for $3.5 billion.

The rating agency also placed under review the credit rating of Sompo International Holdings Ltd, based in Bermuda, which will oversee Aspen once the deal is complete.

The move comes after Sompo Holdings Inc said last week that one of its subsidiaries would acquire all Class A shares of Aspen in an all-cash transaction. The deal is expected to close in the first half of 2026, pending regulatory approval.

AM Best said the review reflects the potential benefits for Sompo’s business profile, including greater global reach and a stronger position in the property and casualty reinsurance market. Aspen is known for its speciality underwriting portfolio and worldwide presence.

Until the acquisition is final and AM Best can fully assess its impact, Sompo’s financial strength rating of A+ (Superior) and issuer credit ratings of “aa-” (Superior) will remain under review.