South Korean President Lee Myung-Bak believes North Korea could detonate multiple devices when it goes ahead with a nuclear test expected in the coming weeks or even days.
In an interview published Tuesday in the Chosun Ilbo daily, the outgoing president also acknowledged the huge challenge the international community faces in seeking to wean Pyongyang off its nuclear weapons programme.
The North has signalled that it will carry out a "higher level" nuclear test very soon, in a defiant response to UN sanctions imposed after its successful long-range rocket launch in December.
Lee said "higher-level" suggested Pyongyang might attempt to detonate several devices.
"North Korea is likely to carry out multiple nuclear tests at two places or more simultaneously" in order to maximise scientific gains from an event that will be globally condemned, Lee said.
Experts around the world are gearing up to analyse any test for what it might reveal about the current status of the North's weaponisation programme.
Of particular interest will be any sign that its scientists have succeeded in developing a warhead that can be fitted onto a missile.
"If the North produces miniaturised weapons that can be used as warheads on missiles, it would really pose a threat," Lee said. "That's why the whole world is watching it so intensively."
Lee has only a few weeks left in office at the end of a five-year term marked by an almost total freeze of contacts between North and South Korea.
In his interview, he suggested that diplomatic efforts would make little headway in bringing about a significant policy shift in Pyongyang.
"I think it is difficult to persuade the North regime to give up the nuclear path," he said.
Some predict the test will come before the Lunar New Year on February 10, while others suggest it will be timed to coincide with the birthday of Kim Jong-Un's father and late leader Kim Jong-Il on February 16.