WASHINGTON (REUTERS) - The United States and South Korea will start a joint exercise called Ulchi Freedom Guardian (UFG) on Aug 21 lasting through to Aug 31, the Pentagon said on Friday (Aug 18), as tensions had escalated over North Korea's missile and nuclear weapons programme.

The statement said about 17,500 US service members would join in the exercise in addition to troops from Australia, Canada, Colombia, Denmark, New Zealand, the Netherlands and Britain.

"UFG is computer simulated defensive exercise designed to enhance readiness, protect the region and maintain stability on the Korean peninsula," the statement said.