About 10 US ships including an aircraft carrier will stage an anti-submarine exercise with South Korea next week in a show of strength to North Korea after the sinking of a warship. Yonhap news agency quoting a military source reports, the USS George Washington will leave its base in the Japanese port of Yokosuka around Saturday and arrive in the Yellow Sea early next week. A spokesman for US forces in Korea declined to comment on the report. The joint drill had initially been planned for late June or early July, but was advanced by about a month to send a strong signal and show off a firm defence posture.<br/>