North Korean leader Kim Jong-il was dead at least 48 hours before U.S. or South Korean officials knew about it, intelligence sources told The New York Times. The report said the death of Kim without Asian and U.S. intelligence knowing about it for so long is the latest in a series of failures to recognize significant events in North Korea -- including Pyongyang\'s construction of an expansive uranium enrichment facility that U.S. officials did not know about until North Korea showed it to a U.S. scientist a year-and-a-half after it was undertaken. Also, North Korea helped develop a nuclear reactor in Syria without Western intelligence knowing of it. With relations between Washington and Pyongyang entering new phase, intelligence officials will have to rely substantially on guesswork for dealing with Kim\'s successor, his son, Kim Jong-un. \"We have clear plans about what to do if North Korea attacks, but not if the North Korean regime unravels,\" Michael Green, a former White House Asia adviser. Christopher Hill, a former U.S. special envoy to North Korea, told the Times the north is \"a society that thrives on its opaqueness.\" Former Obama administration Korea adviser Jeffrey Bader said an unstable transition in Pyongyang, \"in which no one is in charge, and in which control of their nuclear program becomes even more opaque,\" would be worse than a smooth transition in which \"the people keep starving and they continue to develop nuclear weapons.\"