A subsidiary of Bermuda-based Arch Capital Group Ltd. has sold its US marine insurance business to industry giant American International Group.

AIG, which is beefing up its marine insurance operations, bought the US marine insurance business of Arch Insurance Group Inc for an undisclosed amount.

AIG?s global marine unit will immediately begin servicing new marine insurance policies underwritten by Arch Insurance.

In late June, AIG tapped Ralph Mucerino to run AIG Global Marine and Energy, a new unit that combined two existing subsidiaries.

The new group services the insurance, risk-management, and loss-mitigation needs of marine and energy clients worldwide, previously being served by American International Marine Agency Inc. and the AIG Global Energy division.

Also, AIG hired Richard J. Decker to head the company?s commercial marine portfolio. Decker was formerly president of the Inamar Marine Underwriting Agency, a unit of AIG competitor Bermuda-based Ace Ltd.

Arch shares were up $1.18 to $64.27 in afternoon trading on the New York Stock Exchange.