The drills and rhetoric from the allies are "irresponsibly raising the level of confrontation," Kim Son Gyong, vice foreign minister for international organizations, said in a statement carried by state news agency KCNA.
The United States and South Korea will conduct more than 10 days of large-scale military exercises in March, including amphibious landings, officials from the two countries said on Friday, Reuters reported.
The US and South Korea say the exercises are in self-defense and are necessary to counter the rising threats from North Korea's ballistic missile and nuclear weapons programs, which are banned by UN Security Council resolutions.
North Korea on Saturday blamed the United States for the collapse of international arms control systems and said Pyongyang's nuclear weapons were a just response to ensure the balance of power in the region.
The allies also conducted a combined air drill with an American long-range bomber and South Korean fighter aircraft on Friday, and have been staging weeks of exercises for special rations troops.
"The UN and the international community will have to strongly urge the US and South Korea to immediately halt their provocative remarks and joint military exercises," Kim said.
It is regrettable that the UN has been consistently silent on the exercises, which have a "clear aggressive nature," he said.
Last month Kim issued a statement saying UN Secretary General Antonio Guterres has been "extremely unfair, unbalanced" on North Korea's missile tests.