FACTBOX: Possible scenarios for North Korea

(Reuters) - Mounting speculation North Korean leader Kim Jong-il is ill, possibly seriously, raises questions about who would succeed the reclusive leader of the world's first communist dynasty.

Kim, 66, surprisingly missed his country's anniversary parade on Tuesday and a U.S. intelligence official said he may have suffered a stroke

Following are some scenarios presented by analysts on how the transfer of power might take place in one of the world's most secretive states.

* DYNASTIC SUCCESSION - North Korea could follow the pattern by which Kim Jong-il took over from his father and state founder Kim Il-sung in 1994 and name one of three sons as successor. Kim Jong-nam, 37, and his half-brothers, Kim Jong-chol, believed to be 26, and Kim Jong-eun, born in 1983, have undergone elite education in North Korea and in Europe. But unlike their father, none has been obviously groomed as a successor. Many believe the eldest son fell from grace after being caught, in a blaze of embarrassing publicity, trying to visit Tokyo's Disneyland in 2001 with a fake passport. Jang Song-taek, the 62-year-old husband of Kim Jong-il's sister and fairly recently restored to the inner circle, has also been mentioned as a possible successor or caretaker. Even though he was the named successor, it took Kim about two years to clearly establish his hold on power.

* MILITARY RULE - The military could take over. During his 14-year rule, Kim has used the "Songun" or military-first doctrine to cement his grip on office which he holds with the titles of chairman of the National Defence Commission and the million-strong Korean People's Army, as well as head of the communist Korea Workers' Party. His dead father is officially the country's eternal president. The doctrine has given his military, with what many see as their hardline policies, a strong grip on power. But the military is also seen as riven along generational lines and divided by factions loyal to one or another of Kim's sons.

* COLLECTIVE LEADERSHIP - One of Kim's three sons, Jang or No. 2 leader Kim Yong-nam, 80, could become the figurehead leader of a collective leadership drawn from the Korea Workers' Party, the National Defence Commission, or a coalition from those groups that have a vested interest in maintaining the North Korean system.

* STATE COLLAPSES - The impoverished state effectively falls apart, sending millions across the border into the wealthy and more populous South or across the more open border in the north with China. Its centrally run economy is barely able to function and is always short of food. During the 1990s it suffered prolonged famine. For South Korea that is a worst-case scenario which could wreck its economy and create social upheaval.

* NUCLEAR SECURITY - North Korea, which conducted an underground nuclear test in October 2006, is thought to have processed enough nuclear fuel for six to eight atomic bombs from facilities it has begun dismantling under a six-party nonproliferation agreement. The partial and unverified declaration of its nuclear programs that North Korea gave the United States in June did not include weapons. The size and whereabouts of the North's nuclear arsenal remain a closely guarded secret that would become a matter of urgent concern in any post-Kim scenario for North Korea.

(Reporting by Paul Eckert; Editing by Jonathan Thatcher and Jerry Norton)