North Korea's Kim Jong-Il said ties with China will be unchanged by the "replacement of one generation by a new one," KCNA said Saturday, amid reports he is paving the way for his son to take power.

The reclusive leader, who himself inherited control of the nation from his father Kim Il-Sung, is reportedly grooming his third son, Jong-Un, as leader of the secretive communist state.

"The long-standing DPRK (North Korea)-China friendship will remain unchanged despite the passage of time and the replacement of one generation by a new one as it stood tempest and test of history," he said.

Kim's remarks, reported by the state news agency on Saturday, were apparently made during a rare visit to China this week.

Chinese President Hu Jintao, speaking at a state dinner hosted in Kim's honour, said the traditional friendship is an asset that both countries have a historic responsibility to maintain and improve "along with the passage of time and convey it down through generations," KCNA reported.

Professor Kim Yong-Hyun of South Korea's Dongguk University said expressions of bilateral friendship lasting for generations were commonly used at summits between the two countries.

"However, it is noteworthy that this rhetoric was repeated at a time when the North is believed to be raising Jong-Un as an heir," he told AFP.

"I wouldn't be surprised if the North Koreans, during the visit, briefed the Chinese side on their plan for a possible succession by the son and Chinese people listened to them carefully."

Succession speculation has intensified since Kim senior, 67, suffered a stroke in August 2008. Widespread reports say he has chosen Jong-Un to inherit power.

Information is scant about Jong-Un, the second son of Kim Jong-Il's third wife Ko Yong-Hee. Some reports say Jong-Un, born in 1983, attended an international school in the Swiss city of Berne under a pseudonym.

Kenji Fujimoto, a former personal chef to Kim Jong-Il, has described the son as "a chip off the old block" who closely resembles his father physically and in terms of personality.