The announcement today came as Seoul and Washington prepare to begin talks as early as next week on deploying a more sophisticated US missile defence system in South Korea, known as THAAD.
The US military command in South Korea says that an air defence battery unit from Ft. Bliss, Texas, has been conducting ballistic missile training using the Patriot system with other American forces based at Osan Air Base near Seoul.
Lieutenant General Thomas Vandal, commander of Eighth Army, says "exercises like this ensure we are always ready to defend against an attack from North Korea.