South Korean soldiers take part in a civil defense drill against possible North Korea's attack in Seoul on Tuesday, March 15, 2011. North Korea told a Russian envoy that it is willing to discuss its newly disclosed uranium enrichment program if long-stalled nuclear disarmament talks resume, state media reported Tuesday. (AP Photo/Bang Seung-hae)
**FILE** South Korean activists and defectors from North Korea release balloons with the words "Overthrow Kim Jong-il Dictatorship" in Korean and with leaflets condemning the North Korean leader during a rally at the Imjingak pavilion near the border village of Panmunjom, South Korea, on Feb. 16, the North's national holiday celebrating Mr. Kim's birthday. (Associated Press)
'DEAR LEADER': An image of North Korea's designated leader-to-be, Kim Jong-un (center), is shown on a screen during a performance celebrating the 69th birthday of Mr. Kim's father and current leader, Kim Jong-il. Outside information is increasingly penetrating into the secretive state. (Kyodo News via Associated Press)
A South Korean television station airs a program about North Korean leader Kim Jong-il's birthday, seen on a TV screen at the North Korea exhibition hall of the unification observation post in Paju, South Korea, near the border village of Panmunjom, on Tuesday, Feb. 15, 2011. North Koreans will celebrate their leader's 69th birthday Wednesday, one of the country's most important holidays. The screen reads "Magnificent, Birthday Party" in the Korean language. (AP Photo/Lee Jin-man)
North Korean refugee Lee Dong-woon, 82, left center, and his family members pay to respect for their ancestors in North Korea in front of the barbed wire fence as they celebrate the Lunar New Year at the Imjingak Pavilion, near the demilitarized zone of Panmunjom, in Paju, South Korea, Thursday, Feb. 3, 2011. About 32 million people will visit their hometowns during the five-day holiday that begins Wednesday. (AP Photo/Ahn Young-joon)
** FILE ** Stephen Bosworth, the U.S. special envoy for North Korea, talks to the media after meeting with South Korean officials at the Foreign Ministry in Seoul on Wednesday, Jan. 5, 2011. (AP Photo/Ahn Young-joon)
Tens of thousands of North Koreans attend a New Year's rally to display loyalty to leader Kim Jong-il in the central Kim Il-sung Square in Pyongyang, North Korea, on Monday, Jan. 3, 2011. (AP Photo/APTN)
South Korean President Lee Myung-bak looks at North Korea through binoculars Thursday from Yanggu, north of Seoul, as his army and air force staged their largest firing drills of the year.
South Korean Ahyeon Middle School students take shelter at a subway station in Seoul on Wednesday during a simulated attack by North Korea. Their signs read, "A shelter for the 5th class of 3rd grade."
Japanese Foreign Minister Seiji Maehara (left), Secretary of State Hillary Rodham Clinton and South Korean Foreign Minister Kim Sung-hwan observe a moment of silence for the victims of the latest attacks in South Korea by North Korea before the start of their trilateral meeting at the State Department on Monday. (Associated Press)
** FILE ** South Korean President Lee Myung-bak has a briefing with the Joint Chiefs of Staff in Seoul on Tuesday, Nov. 23, 2010, as the military was put on top alert after North Korea's artillery attack on the South Korean island of Yeonpyeong. (AP Photo/Yonhap, File)
Former South Korean marines burn images of North Korean leader Kim Jong il, right, and his son Kim Jong Un, during a rally denouncing North Korea on Saturday, Nov. 27, 2010, in Seoul, South Korea. South Korea is gearing up for joint military maneuvers with the U.S. starting Sunday that are likely to keep tensions soaring following the attack on a South Korean island, which killed two two marines and two civilians. (AP Photo/Wally Santana)
An anti-North Korea protester threatens police trying to extinguish burning icons of North Korea during a demonstration on Friday, Nov. 26, 2010, in Seoul, South Korea. Fresh artillery shots were heard Friday on the tense South Korean island of Yeonpyeong, three days after it was devastated by a North Korean attack and hours after Pyongyang warned that the peninsula was on the brink of war. (AP Photo/Wally Santana)
An unidentified relative of Seo Jeong-woo, a South Korean marine killed on Yeonpyeong Island by North Korea's artillery attack, weeps during a memorial service at a military hospital Wednesday. (Associated Press)