US and Japanese forces began military maneuvers on Friday, heaping pressure on North Korea which Secretary of State Hillary Clinton said posed an "immediate threat" to the region and a long-term threat to the world.
The Republic of Korea (RoK), which joined US forces in military drills this week days after North Korea shelled a South Korean island, has for the first time joined the maneuvers as an observer.
The maneuvers will involve about 44,500 military personnel from both countries in waters east of the southern island of Okinawa, home to a controversial US military base, and elsewhere.
About 60 ships, including the nuclear-powered aircraft carrier USS George Washington and 400 aircraft, will take part in eight days of drills. (Reuters)