** 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)
Protesters denounce North Korea in front of the Defense Ministry, Wednesday, Nov. 24, 2010 in Seoul, South Korea. South Korea's troops were on high alert Wednesday as their government exchanged threats with rival North Korea following a frightening military skirmish that ratcheted tensions on the peninsula to new extremes. (AP Photo/Wally Santana)
Protesters march with defaced portraits of North Korea leader Kim Jong Il, left, and his son Kim Jong Un, denouncing North Korea's artillery barrages targeting Yeonpyeong island Wednesday, Nov. 24, 2010 in Seoul, South Korea. (AP Photo/Kyodo News)
South Korean Marines who injured on South Korean Yeonpyeong Island after being hit by North Korea's attack, sit on beds at a military hospital in Seongnam, South Korea, Wednesday, Nov. 24, 2010. South Korea found the burned bodies Wednesday of two islanders killed in a North Korean artillery attack, marking the first civilian deaths in the incident and dramatically escalating the tensions in the region's latest crisis. (AP Photo/Yonhap)
A South Korean Marine stands beside a crater caused by North Korea's shelling at the Marine Corp's barracks on Yeonpyeong island, South Korea, Wednesday, Nov. 24, 2010. Rescuers found the burned bodies Wednesday of two islanders killed in a North Korean artillery attack, the first civilian deaths from a skirmish that marked a dramatic escalation of tensions between the rival Koreas. (AP Photo/Yonhap)
BRINK OF WAR: South Koreans watch smoke rising from South Korea's Yeonpyeong Island near the border with North Korea on Tuesday. The North fired artillery barrages onto the island. South Korea returned fire and launched fighter jets. (Associated Press)
** FILE ** South Korean President Lee Myung-bak attends a briefing at the Joint Chiefs of Staff in Seoul in November 2010 as the military was put on top alert after North Korea's artillery attack on a South Korean island of Yeonpyeong. (Associated Press)
In this image take from TV footage, smoke rises from South Korea's Yeonpyeong island near the border against North Korea, Tuesday, Nov. 23, 2010. North Korea shot dozens of rounds of artillery onto the populated South Korean island near their disputed western border Tuesday, military officials said, setting buildings on fire and prompting South Korea to return fire and scramble fighter jets. (AP Photo/YTN via APTN)