sovereignty over Dokdo," Yonhap News Agency reported.

South Korea's coast guard said it has deployed more than 18 ships, including patrol vessels, near the isles to block the Japanese ships from entering South Korea's EEZ.

Song Min Soon, Roh's chief security adviser, said South Korea is preparing for a possible confrontation if Japan pushes ahead with its plan to survey the contested area.

"A government vessel maintains its status as a government vessel when it maintains its dignity as one and pays due respect to its host countries, and if it crosses that line, a confrontation is unavoidable," Song was quoted as telling reporters by Yonhap.