The upcoming exercises are expected to involve about 17,500 US servicemen including around 3,000 forces outside of South Korea. Last year, the drills brought in some 25,000 US soldiers including about 2,500 forces from the US mainland and the US Pacific Command.

Some 50,000 South Korean forces will join the drills, according to the ministry.

It is not known whether the US would send strategic assets to the Korean Peninsula.

North Korea on Thursday accused the South and the United States of driving the situation on the divided peninsula into a "catastrophe" by holding joint military exercises against it.

Tensions between the North and the US had heightened amid exchanges of bellicose rhetoric between US President Donald Trump and the North Korean leadership.

Pyongyang had threatened to fire four ballistic missiles toward the waters off the US territory of Guam, but it backed off its threat Tuesday after key US officials dismissed the risk of imminent war with the North.

North Korean leader Kim Jong-un said Tuesday that he will watch Washington's behavior "a little more," but he will make an "important" decision if the US continues its "extremely dangerous reckless actions" on the divided peninsula.

Guam, more than 3,000 kilometers southeast of North Korea, is a base for numerous high-profile US military weapon systems, including strategic bombers, as well as the THAAD missile defense system. The North is sensitive to Washington's dispatch of strategic assets.

His remark seemed to refer to the planned military drills between Seoul and Washington. The allies stressed that the drills are defensive in nature.

"Plans for the exercises were finalized months earlier," said an official at the Ministry of National Defense. "We have not considered whether to adjust the size of the drills." (Yonhap)