The brother of North Korea's new dictator says he believes the collapse of the regime in Pyongyang is inevitable.
Kim Jong-nam is the older half-brother of North Korea's new leader, Kim Jong-un.
In a book based on email exchanges and interviews with Kim Jong-nam, which will be released in Japan later this week, he says the North Korean military has become so powerful it will likely step in and take power from his younger brother.
He says the 28-year-old Kim Jong-un is merely a puppet of the elites and warns North Korea is very unstable.
"My father governed the country with the backing of the military, but the power of the military has become too strong," he told author Yoji Gomi, who interviewed him at length in the Chinese territory of Macau last year.
"If the succession ends in failure, the military will wield the real power for sure."
Kim Jong-nam says North Korea's troubled state-managed economy presented the regime with a dilemma.
"It is obvious that (the) economy will collapse without reforms, but the reforms will lead to a crisis of the collapse of the regime," he said in the interview carried out before the death of his father on December 17.
He also claimed his inexperienced brother was likely to be merely a symbol used by ruling elites to maintain their grip on power.
"Anyone with normal thinking would find it difficult to tolerate three generations of hereditary succession," he said in an email, which Gomi says was sent on January 3.
"I question how a young heir with two years (of training as a successor) would be able to inherit... absolute power.
"It is likely that the existing power elites will succeed my father by keeping the young successor as a symbol."
Kim Jong-nam has lived in virtual exile in China for many years after falling out of favour with his father after being caught trying to enter Japan on a fake passport.
Two years ago and with his health rapidly deteriorating, Kim Jong-il moved Kim Jong-un - believed to be in his late 20s - into the position of designated successor, giving him military posts and raising his profile.
Kim Jong-nam did not directly respond to questions over whether he attended the elaborate funeral and memorial ceremony for his father, but Japanese media have said he visited Pyongyang after learning about his father's death.
Gomi said Kim Jong-nam may still take the reins of power in the secretive state with the backing of Beijing, which frets that a collapse in the regime could send millions of starving North Koreans over its border and create nuclear havoc on the peninsula.
The author said he had decided to go ahead with publishing the book despite requests from Kim Jong-nam for a delay.