WASHINGTON - The planned summit next month between the United States and North Korea is unlikely to see the communist regime give up its nuclear weapons, said a former US nuclear negotiator.

Casting doubt on the prospects of North Korea's denuclearisation, Dr Victor Cha tried to play down expectations that the June 12 meeting between US President Donald Trump and North Korea leader Kim Jong Un could lead to a breakthrough in the nuclear impasse, South Korea's Yonhap news agency reported.

"In terms of the substance, the key issue is, are they going to give up their nuclear weapons? And I think, unfortunately, the answer is no," Dr Cha, former Asia director on the White House National Security Council, said in an interview with US television network NBC.

"I mean, 56 years ago the North Koreans started landscaping the area where they built this nuclear programme. And on Dec 12 of last year they said we've accomplished what we wanted. So three months later they're all of a sudden going to give it all up? It just doesn't make a lot of sense to me," Dr Cha said, according to Yonhap.

Dr Cha is well-known in Washington's foreign policy circles. He participated in the Six-Party talks with North Korea as the deputy head of the US delegation. He is now the Korea chairman at the Centre for Strategic and International Studies think tank in Washington.

The unprecedented summit between Mr Trump and Mr Kim was set for June 12 in Singapore.

What the North Koreans really want, said Dr Cha, is a peace treaty with the United States that would formally end the 1950-53 Korean War, which ended in a truce, not a peace treaty.

"They want a peace treaty because it validates them as a nuclear weapon state," said Dr Cha, as quoted by Yonhap. "It ensures that Trump won't attack because we were worried about an attack last year."

He added: "And most importantly, it means money. Not because the United States is going to give money to North Korea, but we are the primary obstacle in places like the World Bank and the Asian Development Bank, the IMF, where the North Koreans want money."