North Korean leader Kim Jong-un's younger sister is likely to be promoted to a minister-level post within the Workers' Party of Korea during the party's key congress slated for later this week, South Korean experts predicted Thursday.

Kim Yo-jong, believed to be 29, is most likely to be named to a minister-level post within the WPK as the country plans to hold the first party congress in 36 years on Friday, they said.

She is now known to serve as a deputy director within the WPK's Central Committee in charge of the party's propaganda activities.

"There is a high possibility that Kim Yo-jong will be promoted to the director as she has built field experience by helping Kim Jong-un over the past three years," said Yang Moo-jin, a professor at the University of North Korean Studies.

She has been playing a key role in the party's propaganda and agitation department following a series of party reshuffles and the presumed retirement of a party head from the propaganda bureau last year.

Experts further predicted that if the sister's promotion is confirmed, the move is expected to help her brother cement his tight grip on the North.

The party congress is likely to serve as a key event that will reveal the North Korean leader's policy direction in his fifth year in power. Kim inherited power following the sudden death of his father Kim Jong-il in late 2011. (Yonhap)