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On board USS George Washington in S Korea navy drill

25 July 2010 Last updated at 15:23 BST

The US and South Korea have begun a major military exercise in the Sea of Japan, despite threats of retaliation from North Korea.

Washington and Seoul say they want to send a clear signal to the North following the sinking of a South Korean warship in March.

The BBC's John Sudworth reports from on board the USS George Washington warship.