GETTYWorld War 3: The military drills were postponed for the Olympics
The Foal Eagle and Key Resolve exercises are usually held every year around March but they were postponed this year until after the Pyeongchang Winter Olympics and Paralympics, which started in February and ended last month.
They were also postponed to help create conditions for resumption of talks between the two Koreas.
South Korean defence minister Song Young-moo said: “The exercise was postponed according to the spirit of the Olympics.
"We have agreed to uphold the basis until after the Paralympics.”iPhone transfer software Related articles
A Pentagon spokesman said in March that the two joint drills would involve about 23,700 US troops and 300,000 South Korean forces.
Military officials in Seoul said the scale of the exercises would be the same as previous years and would not go beyond.
The Foal Eagle field exercise, which usually involves combined ground, air, naval and special operations troops, will continue for a month.
The computer-simulated Key Resolve will be held for two weeks starting in mid-April.
GETTYWorld War 3: Officials said the scale of the exercises would be the same as previous years
North Korea, which has traditionally accused both South Korea and the United States of practising invading the North during joint military drills, has remained quiet.