North Korean leader Kim Jong-il's health failure poses a challenge for South Korea, the United States and other powers with security interests on the Korean Peninsula due largely to the North's emergence as a nuclear weapons state, reported Yonhap News Agency.

Foreign policy experts say it is impossible to predict who might take over for the leader of the isolated, destitute state, or what impact Kim's absence might have on the multilateral talks on ending the North's nuclear ambitions.

The biggest stakeholder clearly is South Korea, which has had a roller-coaster relationship with the North since the end of the Korean War in 1953.

Bruce Klingner, a senior research fellow at the Heritage Foundation, said the worst-case scenario might be "regime collapse" and an "implosion that draws South Korean or Chinese military units into North Korea to stabilise the situation".

In remarks to Yonhap by e-mail, he added, "US-South Korean contingency planning withered under previous President Roh Moo-hyun and may not have yet recovered under the new administration in Seoul."

The liberal governments of Roh and Kim Dae-jung were often at odds with the US in their more independent stance on the North Korean nuclear issue, the US-South Korean alliance and other national security issues, although incumbent pro-US President Lee Myung-bak has narrowed the gap.

China, the North's biggest benefactor, has maintained the greatest influence in the North in terms of economy, politics and the military. Beijing maintains an alliance that calls for automatic military involvement in any conflicts.

Complicating the situation is North Korea's suspected possession of several nuclear warheads, made from plutonium produced at its Yongbyon nuclear reactor. North Korea detonated is first nuclear device in 2006.

North Korea stopped disabling the reactor on August 14, the day Kim Jong-il disappeared from public view, and reportedly began restoring it, citing US reluctance to remove Pyongyang from its terrorism blacklist.

That coincidence gave rise to speculation that the North's military, displeased with the nuclear talks, took advantage of Kim's illness to undercut the agreement despite the desire by technocrats to reap reciprocal economic benefits. -The Korea Herald, ANN