The current whirlwind of diplomacy and negotiations will not end with "a sincere and complete disarmament" but with "a reduced North Korean nuclear threat", said Thae Yong-ho, who fled his post as the North's deputy ambassador to Britain in August 2016.
"In the end, North Korea will remain 'a nuclear power packaged as a non-nuclear state'," Thae told the South's Newsis news agency.
His remarks come ahead of an unprecedented summit between Kim and Trump in Singapore on June 12 where North Korea's nuclear and missile programmes are expected to dominate the agenda.
North and South Korea affirmed their commitment to the goal of denuclearisation of the peninsula at summit last month, and Pyongyang announced at the weekend it will destroy its only known nuclear test site next week.
But it has not made public what concessions it is offering.
Washington is seeking the "complete, verifiable and irreversible denuclearisation (CVID)" of the North and stresses that verification will be key.
Pyongyang has said it does not need nuclear weapons if the security of its regime is guaranteed.
But Thae, one of the highest ranking officials to have defected in recent years, said: "North Korea will argue that the process of nuclear disarmament will lead to the collapse of North Korea and oppose CVID."
The North wanted to ensure Kim's "absolute power" and its model of hereditary succession, he added, and would oppose intrusive inspections as they "would be viewed as a process of breaking down Kim Jong Un's absolute power in front of the eyes of ordinary North Koreans and elites".
At a party meeting last month when Kim proclaimed the development of the North's nuclear force complete and promised no more nuclear or missile tests, he called its arsenal "a powerful treasured sword for defending peace".
"Giving it up soon after Kim Jong Un himself labelled it the 'treasured sword for defending peace' and a firm guarantee for the future? It can never happen," Thae said.
In his memoir that hit shelves Monday, Thae added: "More people should realise that North Korea is desperately clinging to its nuclear programme more than anything."
Trump last year threatened the North with "fire and fury".
But since the Winter Olympics in the South, Pyongyang and Washington have agreed to the unprecedented Singapore meeting.
Kim has also twice visited China after not paying his respects to President Xi Jinping in the six years since he inherited power from his father, and met the South's President Moon Jae-in in the Demilitarized Zone that divides their countries.
North Korea's sudden change in attitude was probably driven by the mounting international sanctions imposed over its weapons programmes that had begun to take a toll on the livelihoods of ordinary citizens, Thae said.
As of last year the UN Security Council sanctions included measures on sectors such as coal, fish, textiles and overseas workers.
"North Korea did not foresee the destructive power of these sanctions," Thae told the interview. "These sanctions are threatening the livelihoods of millions of North Koreans at the root."
But Pyongyang had a long history of making overtures that ultimately came to nothing, he warned.
"North Korea's diplomacy has always been a repeat of hardline and appeasement," Thae said.
"It is North Korea's diplomatic tactic to push the situation to extreme confrontation and suddenly send peace gestures."
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)