The United States and South Korea will kick off their Ulchi Freedom Shield large-scale joint military exercise this month, both countries announced Thursday.

South Korea and the United States will conduct major joint military drills starting on August 18, officials said, although they will delay parts of the annual exercises that have been a source of tension with North Korea to later in the year.

The Aug. 18-28 exercise may trigger an angry reaction from North Korea, which calls the joint drills invasion rehearsals.