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 is scheduled for two weeks starting in mid-April.
Foal Eagle will be participated in by some 300,000 troops from South Korea and 11,500 from the United States.
Subsequently, Kim is expected to meet U.S. President Donald Trump for the first-ever summit between the two countries, though the date and venue have yet to be determined.
The decision to cut short the exercises seems to be aimed at maintaining the current climate warming relations with North Korea, which views the drills as a rehearsal for invading its territory, and amid plans for two historic summits between North Korean leader Kim Jong-un and the presidents of South Korea on April 27 and the U.S. in May.
During last year's Foal Eagle exercises, the North launched a number of ballistic missiles.
The allies are holding the drills later than usual this year after postponing them to help pave the way for the North's participation in the Olympics and Paralympics, which were held in the alpine town of Pyeongchang.
Close A Marine Corps pilot prepares for a vertical landing of a F-35B stealth fighter aboard the USS Wasp amphibious assault carrier
Tension on the flashpoint peninsula has shown signs of easing after the nuclear-armed North proposed summits with the South and their "imperialist enemy" the US. The North has fiercely objected to the drills in the past, calling them a rehearsal for an invasion.
The United States agreed to the change so as not to provoke North Korea, which sent athletes, artists and a government delegation to the Games.
Defense Secretary Jim Mattis and his South Korean counterpart, Song Young-moo, said in a statement earlier this month that the exercises would be held "at a scale similar to that of previous years".
Almost 12,000 US troops and around 300,000 South Korean forces will take part.
Kim Jong Un and South Korean President Moon Jae-in are reportedly expected to discuss denuclearization of the Korean peninsula and improvement of the relations at the upcoming summit.
Relations between the USA and North Korea also appear to be thawing lately.