South Korea on Sunday downplayed North Korean leader Kim Jong-un's vow to "strive for the denuclearization of the world," stressing that the pledge was no different from Pyongyang's erstwhile stance against its own denuclearization.

During the ongoing congress of the ruling Workers' Party of Korea, Kim said that his country would "faithfully" fulfill its obligation for non-proliferation and strive for global denuclearization. He also vowed not to use nuclear arms first unless the North's sovereignty is encroached upon.

"While (he) calls his country a responsible nuclear-armed state, (he) mentioned the denuclearization of the world. That means that (the North) would not seek denuclearization," a senior government official told Yonhap News Agency over the phone, requesting anonymity.

"What the North meant by the denuclearization of the world is that it would abandon its nuclear arms when the entire world gives up nuclear weapons."

He added that there was no "positive message" from Kim's statement.

Pyongyang has already claimed itself to be a nuclear-weapons state, an argument denied by Seoul and Washington. It has long argued that it is pursuing a credible "nuclear deterrence" due to the U.S.' "hostile" policy towards it.

The reclusive state has already called itself a nuclear power in its constitution and adopted a controversial dual-track policy of simultaneously developing nuclear arms and its debilitated economy -- two goals Seoul has said were "incompatible." (Yonhap)