The North Korean representative said ANZUS exists "in name only", and described the August 21 to 31 military drills, Ulchi Freedom Guardian, as "aggressive nuclear exercises of the U.S".
North Korea's Supreme Leader believes it is a way for the South to prepare for an invasion and has previously declared it "little short of a declaration of a war".
South Korean President Moon Jae-in again urged the United States Monday to refrain from taking any action against North Korea that could start an armed conflict on the peninsula, saying even the slightest conflict here may cost the lives of many South Koreans and USA troops.
Moon made the remarks at a meeting at Cheong Wa Dae with a bipartisan group of US lawmakers including Sens.
"It's to prepare if something big were to occur and we needed to protect ROK", said Michelle Thomas, a USA military spokeswoman, referring to South Korea by its official name, the Republic of Korea.
Pyongyang then threatened to fire a salvo of missiles towards the United States territory of Guam - a plan that leader Kim Jong-Un then delayed, but warned could go ahead depending on Washington's next move. -South Korea military exercises demonstrate near the U.S. Embassy in Seoul.
Commenting on the upcoming drills, the North Korean state newspaper Rodong Sinmun reported that the drills would contribute to escalating tensions on the Korean Peninsula.
Korea drills underway as tensions remain high
If North Korea uses the drills this week as a reason to launch missiles around Guam or elsewhere, it could set off a new cycle of escalation. Last year, Pyongyang test-fired a submarine-launched ballistic missile and carried out its largest nuclear test to date. The United States has about 28,000 troops in South Korea.
State media in the North said: The joint exercise is the most explicit expression of hostility against us, and no one can guarantee that the exercise won't evolve into actual fighting.
President Donald Trump has warned that North Korea will face "fire and fury" if it threatens the United States.
About 17,500 USA service members are participating in the exercise this month, down from 25,000 previous year, according to the Pentagon.
Defence Secretary Jim Mattis said on Thursday the USA military would be prepared to intercept any missile heading toward the United States territory or that of its allies.
Yesterday, North Korea warned the USA that it will be "pouring gasoline on fire" by going ahead with the games.
It added: 'If the United States is lost in a fantasy that war on the peninsula is at somebody else's doorstep far away from them across the Pacific, it is far more mistaken than ever'.