President Lee Myung-bak says North Korea is inching towards a critical stage with its nuclear program.

In an interview with the Chosun Ilbo newspaper on Monday, the South Korean leader said Pyongyang will likely conduct multiple, simultaneous nuclear tests at its Punggye-ri nuclear test site as part of an effort to produce smaller nuclear warheads.

Once the North begins testing weapons like these, President Lee said its nuclear program will have entered a dangerous level as it heightens the possibility of Pyongyang selling smaller nuclear devices to Iran or mounting the weapon on its own intercontinental ballistic missile.

Experts had originally expected North Korea to become capable of testing long-range missiles with nuclear warheads in the next seven to 10 years, but if its third nuclear test is successful, they say the capability could be reached as early as sometime in the next four to five years.

With the successful launch of its Unha-3 rocket in December, the United States became the latest country to be within Pyongyang's missile range.

The rocket can travel over 10-thousand kilometers, potentially reaching San Francisco, carrying a warhead weighing up to 600 kilograms.

And should the reclusive state succeed in miniaturizing its nuclear devices, President Lee expects to see a drastic change in Washington's policies regarding North Korea.

The president for his part remains skeptical about the possibility of successfully talking Pyongyang out of its nuclear program.

Hwang Sung-hee, Arirang News.

Reporter : ssung86@arirang.co.kr