Moody's upgraded the senior debt rating to A3 from Baa1 of Endurance Specialty Holdings Ltd., which was rebranded as Sompo International following its acquisition by Japan-based Sompo Holdings Inc.

The rating agency also upgraded the insurance financial strength ratings of Endurance Specialty Holdings' subsidiaries, Endurance Specialty Insurance Ltd. and Endurance Assurance Corp., to A1 from A2.

The outlook is stable.

Endurance Specialty Holdings is a wholly owned subsidiary of Sompo Japan Nipponkoa Insurance Inc., a part of Sompo Holdings.

Moody's said the ratings reflect implicit and explicit support to Endurance Specialty Holdings from its parent company. The rating agency believes that the company is strategically important to the group as part of Sompo Japan Nipponkoa's strategy to grow its specialty platform and diversify outside its domestic Japanese market.

Additionally, the rebranding of the company to Sompo International demonstrates increased reputational ties and operational integration between Endurance Specialty Holdings and Sompo Japan Nipponkoa, Moody's said.