Kim Jong-il dies: Will his son replace him as leader of North Korea?

North Korean leader Kim Jong-il is dead.

A weeping North Korean woman, garbed in black traditional dress, announced Mr. Kim’s death on North Korean television on Monday, two days after he suffered a heart attack while on a train.

His death at the age of 69 leaves an enormous power vacuum in North Korea even though over the past three years he has sought to advance his third son, Swiss-educated Kim Jong-un, in his late 20’s, as his successor.

Kim Jong-un’s ascendancy was signaled clearly on Monday with the announcement that he would be in charge of funeral arrangements for his father, who was known as the “Dear Leader.” The initial mourning period will end on December 29 after which North Korea is likely to retreat into a backstage power struggle whose outcome is far from clear.

“In a situation like that the systems don’t allow for easy adjustment,” says David Straub, former head of the Korea desk at the US State Department.

The transition may be smoothed, however, Mr. Straub notes, by the influence of a core inner circle, including Kim Jong-il’s widow, sister and brother-in-law, as key players along with a coterie of generals who may form a ruling clique behind the throne held by Kim Jong-un.

Kim Jong-il died at a critical moment in U.S.-North Korea relations in which the U.S. was widely reported to be about to announce 250,000 tons in food aid for the first time in three years, while North Korea was reportedly about to announce a moratorium on missile and nuclear testing.

This planned deal is now up in the air.

North Korea had appeared recently to have softened the tone of its rhetoric while preparing for what would have been Kim’s 70th birthday in February and huge celebrations surrounding the 100th anniversary of the birth of his long-ruling father, Kim Il-sung, who died in 1994.

North Korea has conducted two underground nuclear tests, in October 2006 and May 2009 but seemed to have put the threat of a third test on hold while appealing for food aid from the U.S. and South Korea, whose conservative president, Lee Myung-bak, cut off such aid after his inauguration in February 2008.

Mr. Lee called an emergency cabinet meeting Monday, while South Korean troops went on full emergency alert.

The U.S. envoy on North Korean human rights, Robert King, recently met with a top North Korean official in Beijing to talk about food aid. “Now we have a situation where South Korean and U.S. officials have to decide very quickly in terms of public statements,” says Mr. Straub. “They will have to review and regroup on food aid.”

Since the first reports that Kim Jong-il had suffered a stroke in 2008, North Korean officials had gone to great lengths to demonstrate the strength of the man who imposed one-man rule over the country that was just as harsh as was the rule of his father.

His health began to deteriorate sharply after he hosted the late South Korean president, Roh Moo-hyun, at a summit in Pyongyang in October 2007. Mr. Roh had carried on the Sunshine policy of reconciliation between North and South Korea inaugurated by the late Kim Dae-jung, who went to Pyongyang for the first inter-Korean summit in June 2000.

Kim disappeared from public view for six months, but over the past two years had appeared active, engaging in numerous inspection tours of the country and three visits to neighboring China, his country’s closest ally.

The official North Korean news agency KCNA reported that Kim “suffered an advanced acute myocardial infarction, complicated by serious heart shock, on a train on December 17.” The report said that he had been under “great mental and physical strain caused by his uninterrupted field guidance tour for the building of a thriving nation.”