During a closed-door briefing to the National Assembly's intelligence committee, the National Intelligence Service (NIS) offered the assessment amid growing speculation over North Korea's succession plans, fueled by Ju-ae's increasing visibility.
She has taken on an increasingly prominent public role this year, making frequent appearances in North Korean state media including firing a weapon, driving a new main battle tank and standing alongside her father at major events.
The speculation also comes as U.S. President Donald Trump has stepped up overtures toward Kim, saying he expects to meet the North Korean leader later this year while reiterating their "very good" relationship.
The NIS believes Pyongyang may be deliberately exposing Ju-ae to the public to establish her image among North Koreans as a future leader.
Ju-ae has taken on a more prominent public role this year. North Korean state media have shown her firing a weapon and personally driving a new main battle tank. She also appeared alongside her father at a concert in Pyongyang in July marking the 73rd anniversary of what North Korea calls its victory in the Korean War.
Rep. Han Ki-ho of the People Power Party (PPP) said Kim is likely to keep putting his daughter in the public eye to strengthen her position as a possible successor.
"Kim can trust no one but his own children, but she is still young and a girl, so he will continue trying to familiarize the North Korean people with Kim Ju-ae," Han said.
Some lawmakers, however, cautioned that it is still too early to conclude that Ju-ae has been chosen as Kim's successor.
"It is still too early to draw that conclusion," said Rep. Kwon Young-se of the PPP, a former unification minister.
Rep. Kim Gunn of the PPP, a former special representative for Korean Peninsula peace and security affairs at the Ministry of Foreign Affairs, also urged caution.
"We still need to watch the situation further," Kim said. "There are certainly signs that make her look like a successor, but I do not see why the relatively young North Korean leader would already designate the young girl as his successor."
Kim Jong-un is 42, while Ju-ae is believed to be 13.
Rep. Kim Joon-hyung of the Rebuilding Korea Party, a former chancellor of the Korea National Diplomatic Academy, said he disagreed with the NIS assessment.
"At this point, it would be a stretch to conclude that Ju-ae has been confirmed as the successor," he said.
AJP Takeaways
• North Korea's Kim Ju-ae is moving closer to being formally designated as Kim Jong-un's successor, according to South Korea's National Intelligence Service. The NIS cited her increasingly frequent appearances in state media and growing involvement in military and political events.
• Kim Jong-un appears to be building public recognition of his daughter as a potential future North Korean leader. Ju-ae, believed to be 13, has recently been shown firing a weapon, driving a new main battle tank and accompanying her father at major state events.
• South Korean lawmakers remain divided over whether Ju-ae has already been chosen as North Korea's next leader. While the NIS sees growing signs of succession planning, lawmakers including Kwon Young-se, Kim Gunn and Kim Joon-hyung said it is still too early to conclude that the 42-year-old Kim Jong-un has formally selected his daughter as his successor.
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