Pyongyang's state news agency KCNA announced the Korean Workers' Party is to hold its rare congress next week, after much speculation in the South the event would be held either May 2 or May 7.
Delegates from various North Korean cities and counties were selected starting April 17, and April 20 Kim was chosen to represent the military at the congress.
In a written manifesto, the party's Politburo stated Kim is following in the footsteps of his father, Kim Jong Il, and biological grandfather Kim Il Sung by strengthening the party and the revolutionary mission of "Juche," North Korea's philosophy of self-reliance.
In Seoul, the National Intelligence Service said North Korea has finished taking steps toward a fifth nuclear test. Kim only has to say the word, Yonhap reported.
"Tunnels to the [underground] nuclear site and nuclear materials are ready," the spy agency told South Korean lawmakers, according to ruling party politician Lee Cheol-uoo and the opposition's Shin Kyeong-min.
Intelligence officials also said the North's most recent test of a submarine-launched ballistic missile was a success, but because of the amount of investment involved the North could take three to four years to perfect the weapons system.
Pyongyang's next nuclear test is imminent, according to multiple sources, and could take place to be timed with South Korean President Park Geun-hye's state visit to Iran on May 1-4, local newspaper Munhwa Ilbo reported.
Kim Young-soo, a political scientist at Seoul's Sogang University, said the test is most likely to take place between May 3 and 5, when North Korea ends its "70-day battle" or mass rallies, that are taking place ahead of the congress.