On September 10, 2013, the U.S. Coast Guard issued an Advance Notice of Proposed Rulemaking seeking comments on the proposed expansion of safety management requirements to certain vessels operating on the U.S. Outer Continental Shelf. Many vessels operating on the U.S. OCS are already covered by such requirements via the International Convention for the Safety of Life at Sea 1974 (SOLAS) – although other objects defined as "vessels," including offshore supply vessels, accommodation vessels and mobile offshore drilling units, may not be covered. The Coast Guard seeks comments by December 9, 2013 on its proposal to require all U.S.-flag and non-U.S.-flag vessels engaged in OCS activities to develop, implement and maintain a Safety and Environmental Management System (SEMS) based on principles of the American Petroleum Institute's Recommended Practice for Development of a Safety and Management Program for Offshore Operations and Facilities, Third Edition, May 2004. Among the issues the Coast Guard is considering is how the API recommended practices can be harmonized with the International Safety Management (ISM) Code and other similar industry guides which may already apply to certain vessels.