The 32-year-old attended the politburo meeting on July 2 as a full member, according to a report carried in US-backed newspaper Daily NK, which hailed it as a clear indication that she was “solidifying” her position as her brother’s second-in-command. Roy Calley, a frequent visitor to the Hermit State, who wrote about his experiences in the book Look With Your Eyes and Tell the World, likewise believed the move was highly significant.
He told Express.co.uk: “This suggests to me that she is being moved to a position of ultimate power.
“It’s always difficult to know how things work in Pyongyang, but experience suggests that the soft approach from the Supreme Leader no longer has favour.
“Her stance is hard line and you could never imagine her having a cozy chat with Trump.”
A statement attributed to Kim Yo-jong last week suggested she believed another summit meeting with the US President as “unpractical” and would “not serve us at all”.
The statement further suggested no further meetings would take place unless the US made “major changes” to its “attitude” and ended its “hostile policy”.
Mr Calley, who questioned whether Kim Jong-un was still alive after rumours of his death swept the world in April, added: “It’s possible that Kim Jong-un is struggling with health – if he is still alive, which I still question – and she is edging closer to ultimate power.
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With respect to the remarks attributed to Kim Yo-jong about a possible future summit, he said: “It has not been unusual for important statements to come from sources other than the top person.
“Senior Party and government leaders often do so, while others come from the MFA, Party or organisational spokesmen.
“The KCNA news agency often carries authorised statements.
“Under Kim Il-sung, first his brother and later Kim Jong-il often spoke in the leader’s name.”
Neverthless, Prof Hoare said it was clear Kim’s sister, who has been frequently touted as a possible successor in recent weeks, was increasingly influential.
He explained: “Ms Kim is certainly active and it may be that she is staking out a position.
“If there is a debate, perhaps Kim Jong-un is waiting to see what happens and is happy to let her front one side.
“To me the statement was tough but closed no doors – a useful position.”
Kim Jong-un, who is believed to be 36, has been North Korea’s leader since 2011, when he took over from his father Kim Jong-il.
Prior to that, Kim Jong-il himself became leader in 1994 after the death of his father, Kim Il-sung, who founded the secretive communist nation in 1948.
Speaking this week, US Secretary of State Mike Pompeo said another summit meeting between Mr Trump and Kim was unlikely this year.