The US and South Korean militaries have kicked off large exercises to underscore deterrence against North Korea after accusing the reclusive communist state of sinking a warship. Pyongyang warned that the drill had pitched the peninsula onto the brink of war. US naval vessels, including the nuclear-powered aircraft carrier USS George Washington, set off from South Korean ports on Sunday to begin the drills. The war games were called last week in a show of force timed with a high-level meeting between the two allies. North Korea drove tensions to new heights after a team of investigators, led by South Korea's military, accused it of firing a torpedo in March to sink the corvette Cheonan, killing 46 men. The United States announced new sanctions on the North last week, freezing the assets of Pyongyang's leaders it said were earned through illcit activities and cutting off the flow of cash to them. The moves would also ban travel by some individuals. On Saturday, the North's powerful National Defence Commission vowed to launch a "sacred war" against the United States and South Korea at "any time necessary", in response to the drills, denounced as "reckless."