A foreign ministry spokesman said North Korea could not help but link the South's nuclear experiments to six-nation talks which are scheduled to resume this month.

"We cannot but link these cases to the issue of resuming the six-party talks," the spokesman was quoted as telling the official Korean Central News Agency (KCNA).

He said there was strong suspicion that the disclosed experiments might be conducted "at the instruction of the United States as they assume military nature."

"The US has applied double standards as regards the nuclear issue. It has transferred nuclear technology to its 'allies' and connived at their nuclear weapon-related activities and possession of nukes," he said.

"What matters is whether the United States intends to overlook South Korea's development of nuclear weapons as it did that of Israel."

"South Korea is under US nuclear umbrella. It is self-evident that the DPRK (North Korea) can never abandon its nuclear program under such situation," he added.

He indicated that Pyongyang might not attend the six-nation talks -- also including the United States, China, Japan and Russia -- until the South clears its name before the international community over the disclosed nuclear experiments.

"The cases should be clarified transparently and thoroughly and necessary measures be taken. We will closely follow the expected results of the investigation," the spokesman said.

South Korea admitted over the past week that its scientists produced a miscroscopic amount of enriched uranium in a lab experiment in 2000 and also extracted a tiny amount of plutonium in 1982.

But it said the experiments were purely for academic purposes and denied it had any weapons programmes.

The stand-off flared in October 2002 when the United States accused Pyongyang of operating a nuclear weapons program based on enriched uranium, violating a 1994 agreement.

Pyongyang has denied running the uranium-based program but has restarted its plutonium program.