Nissay Dowa General Insurance Co. said Monday it has agreed in principle to form an alliance with U.S. insurer St. Paul Companies Inc. to better serve each other's customers.

A formal agreement is expected to be made in January, the Japanese casualty insurer said.

Under the agreement, Minnesota-based St. Paul will provide insurance services on behalf of Nissay Dowa's customers in the United States, while the Japanese firm will do the same on behalf of St. Paul's corporate customers in Japan.