North Korea is raising the level of its military threat as South Korea and the U.S. are set to begin their largest-ever joint military exercises.

The North’s official Korean Central News Agency(KCNA) released a statement by Pyongyang's National Defense Commission Monday that vowed to "take military counteraction for preemptive attack."

The statement comes as the Key Resolve and Foal Eagle exercises are set to begin in South Korea.

The North has repeatedly said that the annual joint exercises are considered as a challenge to its sovereignty and provocation of a nuclear war.

Monday's statement also said that North Korea's nuclear attack capabilities were on constant alert, ready to hit key targets in South Korea, U.S. military bases in the Asia-Pacific and the continental United States.