In a commentary carried by the official Rodong Sinmun newspaper, the North warned of an "uncontrollable phase of a nuclear war" on the peninsula.
They are described as defensive, but nuclear-armed Pyongyang views them as a highly provocative rehearsal for invasion.
"North Korea will conduct a sixth nuclear test in order to bring the United States to negotiations", said Yoo Ho-yeol, professor of unification and diplomacy at Seoul's Korea University.
Both US Secretary of State Rex Tillerson and Secretary of Defense James Mattis announced last week that they were keeping military options on the table in dealing with North Korea.
But Moon said Seoul effectively had a veto on military action by the USA, its security ally and protector.
Just last week, Pyongyang said it had finalized a plan to fire four missiles toward the USA territory of Guam. Troops from Australia, Canada, Colombia, Denmark, New Zealand, the Netherlands and the United Kingdom will join in as well.
With tensions high on the Korean peninsula, China - Pyongyang's main ally and trading partner - has urged the United States and South Korea to scrap the drills, as has Russian Federation.
"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", the editorial read, according to South Korea's Yonhap News Agency.
Last month North Korea test-launched two ICBMs at highly lofted angles, and outside experts say those missiles can reach some USA parts like Alaska, Los Angeles or Chicago if fired at normal, flattened trajectories. In 2015, North and South Korea exchanged artillery fire at the same time as the Ulchi Freedom Guardian drills after the South began blasting propaganda on loudspeakers across the border. But he added that the diplomatic approach "has to be backed with military threat" if North Korea chooses to move forward with destabilizing actions.
During last year's Ulchi drills, North Korea test-fired a submarine-launched ballistic missile that flew around 310 miles - the longest flight by that type of weapon.
"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", it said.
"Kim Jong Un might make the logical decision that it's probably bad to test during a military exercise", Kazianis said.
Robert Gallucci, the chief US negotiator during the 1994 North Korean nuclear crisis, said the exercises are important for the USA and South Korean alliance and that no change should be made to them unless South Korea wants to.