A leading U.S. defense contractor Lockheed Martin is reported to be upgrading the performance of six U.S. Aegis-class destroyers in detecting missiles being launched from North Korea.

Bloomberg news agency said Saturday the warships will be deployed off South Korea's east coast in September.

It quoted Lockheed Martin officials as saying the upgrade was for processors on the destroyers that will allow for detection, tracking and possible deterrence of medium- and long-range missiles.

North Korea rattled nerves in the region when it test-fired a ballistic missile in 1998, sending it over Japan and into the Pacific Ocean.