Thae Yong-ho was quoted on Monday as saying that North Korean leader Kim Jong-un "will drag on for two to three years" without dismantling his nuclear weapons "while waiting for the U.S. president to be replaced."

The former No. 2 man in the North Korean Embassy in London and now a vocal critic of the regime, has predicted Pyongyang will drag out talks about its nuclear program as long as possible while extracting concessions.

He was giving a lecture at the Mulmangcho Foundation, an organization aimed at helping North Korean defectors settle here, last Friday.

"Kim will act during his summits with Seoul and Washington as if he were determined to dismantle nuclear weapons in stages -- first declaring dismantlement followed by incapacitating nuclear weapons and denuclearization," it quoted Thae as saying.

But while extracting concessions at each stage, the regime "can never abandon its nuclear weapons because it proclaims itself a nuclear state in its Constitution."

Thae said fresh UN sanctions against the North that started last September "have proved more powerful than any other sanctions of the last decade. Feeling a sense of crisis, Kim Jong-un rushed to Beijing to seek help, but it seems that he failed to achieve satisfactory results."

He warned that peaceful coexistence or reunification under a federal system "is impossible without denuclearization."

Thae said if Seoul makes concessions to the North, like lifting some sanctions or reopening the joint-Korean Kaesong Industrial Complex, it "should strongly demand improvement of human rights in return."

