|Kim, centre, announced his son's promotion to two powerful posts, confirming him as heir-apparent [AFP/HO/KCNA]
Kim Jong-il, the North Korean leader, has announced his youngest known son's appointment to two important political posts, according to state media, in what is regarded as the first step in his much-anticipated succession plan.
The move coincided with South Korea's announcement it will hold working-level military talks with North Korea later this week - the first such meeting in two decades.
The promotion of Kim Jong-un, in his 20s, to the rank of four-star general could make the relative unknown the next North Korean leader.
His appointment was made public on Tuesday in advance of North Korea's biggest political convention in three decades.
North Korea's official news agency early on Wednesday said Jong-un was named a vice-chairman of the Central Military Commission of the Workers' Party, and a member of the Party's Central Committee.
Speculation about a dynastic succession has swirled since Kim reportedly suffered a stroke in August 2008.
In Washington, PJ Crowley, a US state department spokesman, compared the situation to a television show, and said it was too early to reach any conclusions.
"I would suppose this is perhaps the ultimate reality show unfolding in North Korea and we are simply watching this very closely," he said.
"It's a bit too early to assess what the implications are."
Al Jazeera's Tony Birtley, reporting from Seoul, said Kim Jong-il appears to be building the political support base for his son, although it was not clear whether Jong-un will be officially named as successor during the party meeting.
Regarding the talks, our correspondent said there was a slight thawing in relations between the two Koreas, as seen from South Korea's announcement on Wednesday of a $8.5bn aid package for flood victims in the North.
In announcing the meeting planned, South Korean media citing the defence ministry said three officers from each side will meet on Thursday in the truce village of Panmunjom in the Demilitarised Zone dividing the peninsula.
The last such military talks were held in October 2008.
North Korea had earlier this month proposed the military talks to discuss the two countries' disputed western maritime border and anti-North Korean leaf-letting activities by South Koreans.
The poorly marked sea border, drawn by the United Nations at the end of the 1950-53 Korean War, is a constant source of tension between the two sides.
South Korea has repeatedly rejected the North's long-standing demands that the sea border be changed.