United States Naval Ship

(DOD) A public vessel of the United States that is in the custody of the Navy and is: a. Operated by the Military Sealift Command and manned by a civil service crew; or b. Operated by a commercial company under contract to the Military Sealift Command and manned by a merchant marine crew. Also called USNS. See also Military Sealift Command.
Source: JP 4-01.2