Kim said he highly valued the officials trained under his father, the late President Kim Il Sung, but as most are now well past 70, it is time to employ new, younger leaders.
The quotations were found in a book published in North Korea in September and recently obtained by Yonhap. The book is a collection of documents, letters and speeches by Kim Jong Il, dated from January 2000 to December 2004.
Since inheriting power upon his father's death in 1994, the younger Kim has retained as key leaders many of his father's colleagues.
The North Korean leader also suggested that new officials should have an academic background, a previously unnecessary requirement in a state where loyalty is the highest value and individual abilities and achievements are downplayed.
"We must now stress people's academic background in all walks of life," Kim was quoted as saying. He also said an official's remarks could be taken seriously only if they were backed up by knowledge.