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

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