Kim Jong Un, North Korean leader Kim Jong Il's youngest son, has been promoted to general, the state news agency reported, a step believed to be the begining of a process by which he will take over for his father.
This is the first time that the son's name has been uttered in public. There has been a whisper campaign that he would be the successor for some time, but he has not been named successor yet.
The meeting Tuesday of the ruling Worker's Party is the biggest in 44 years and may further pave the way for Kim Jong Un. He is approximately 27 years old - no one knows his age for sure - and has been known as the "Young General" or "Our Commander" for some time.
Kim Jong Il had no military experience when he assumed power but is known as "The General."
Until now, the son had held merely a low-level post on the National Defense Commission - the ruling military body that really runs the country.
U.S. Assistant Secretary of State Kurt M. Campbell said in a conference call that Washington was "watching developments carefully" and was working to interpret the announcement's significance.
The question of who will take over from Kim Jong Il, who rules with absolute authority but is believed to suffer from a host of ailments, is important to regional security because of North Korea's active nuclear and missile programs, and regular threats it makes against rival South Korea.
Many delegates to the party meeting arrived in Pyongyang on Sunday by train and the city was festooned with flags and placards announcing the event, footage shot by video news service APTN showed. "Warm congratulations to the representatives meeting of the Workers' Party of Korea!" read one poster.
Kim Jong Il took control of North Korea when his father, the North's founder Kim Il Sung, died of heart failure in 1994. He has reportedly groomed third son Kim Jong Un as his heir to power.
A South Korean newspaper reported Monday that the younger Kim was chosen as a military delegate to the conference. The party central committee then put out internal propaganda proclaiming him to be Kim Jong Il's sole successor, the Chosun Ilbo newspaper said, citing a source in North Korea that it did not identify.
Still, some experts said Kim's son may not be ready to officially debut as a successor, which could make the 68-year-old leader promote his sister to a prominent position to help Kim Jong Un eventually run the North.
Kim Kyong Hui, who is married to Russian-educated Jang Song Thaek, vice chairman of the all-powerful National Defense Commission, has emerged as one of Kim's key aides in recent years, experts said.
Kim Jong Il might designate his 64-year-old sister to serve as a caretaker for the third-generation successor after Kim's death, former Japanese Defense Minister and national security adviser Yuriko Koike wrote in a syndicated column earlier this month.
Fox News' Justin Fishel and the Associated Press contributed to this report.