SEOUL, South Korea and the United States have staged a combined marine warfare exercise in the East Sea to hone their skills in deterring maritime security threats and ensuring safe navigation in the sea, the South's Navy said Tuesday. The annual drill kicked off on April 1 for a nine-day run in waters off Pohang, 262 kilometers southeast of Seoul, involving nine naval ships and four helicopters from the two nations. The U.S. dispatched an expeditionary sea base, USS Miguel Keith (ESB 5), for the first time, which was joined by two other naval ships and MH-53 helicopters. The 240-meter vessel Miguel Keith is designed to provide a floating helicopter landing base, and provide other support to military operations as an expeditionary sea base. South Korea mobilized six ships, including a Nampo MLS-II minelayer, as well as a P-3 maritime patrol helicopter and a UH-60 chopper. "The drill was designed to train the South Korean and American navies to practice procedures and tactics for clearing paths for safe n avigation and strengthen their joint response capabilities against complicated mine warfare scenarios," the South Korean Navy said in a release. The combined drill staged various exercises to hone skills in laying, detecting and removing mines, providing logistics support and helicopter's landing on a vessel to practice sailors' capabilities to protect key ports and maritime traffic routes in similar situations, it noted. Source: Yonhap News Agency