Security Council members vote for tough new sanctions against North Korea for its latest nuclear test, during a meeting at U.N. headquarters Thursday, March 7, 2013. The unanimous vote by the U.N.'s most powerful body sparked a furious Pyongyang to threaten a nuclear strike against the United States. (AP Photo/Bebeto Matthews)

Russia’s UN Ambassador Vitaly Churkin, center, current president for the U.N. Security Council, confers before leading council members on a vote for tough new sanctions against North Korea for its latest nuclear test, during a meeting at U.N. headquarters Thursday, March 7, 2013. The unanimous vote by the U.N.'s most powerful body sparked a furious Pyongyang to threaten a nuclear strike against the United States. (AP Photo/Bebeto Matthews)

U.K. Ambassador Mark Lyall, left, and U.S. Ambassador Susan Rice confer before members of the United Nations Security Council vote for tough new sanctions against North Korea for its latest nuclear test, during a meeting at U.N. headquarters Thursday, March 7, 2013. The unanimous vote by the U.N.'s most powerful body sparked a furious Pyongyang to threaten a nuclear strike against the United States. (AP Photo/Bebeto Matthews)

U.K. Ambassador Mark Lyall, left, and U.S. Ambassador Susan Rice confer before members of the United Nations Security Council vote for tough new sanctions against North Korea for its latest nuclear test, during a meeting at U.N. headquarters Thursday, March 7, 2013. The unanimous vote by the U.N.'s most powerful body sparked a furious Pyongyang to threaten a nuclear strike against the United States. (AP Photo/Bebeto Matthews)

North Koreans attend a rally in support of a statement given on Tuesday by a spokesman for the Supreme Command of the Korean People's Army vowing to cancel the 1953 cease-fire that ended the Korean War as well as boasting of the North's ownership of "lighter and smaller nukes" and its ability to execute "surgical strikes" meant to unify the divided Korean Peninsula, at Kim Il Sung Square in Pyongyang, North Korea, on Thursday, March 7, 2013. North Korea on Thursday vowed to launch a pre-emptive nuclear strike against the United States, amplifying its threatening rhetoric hours ahead of a vote by U.N. diplomats on whether to level new sanctions against Pyongyang for its recent nuclear test. (AP Photo/Jon Chol Jin)

North Koreans attend a rally to support a statement given on Tuesday by a spokesman for the Supreme Command of the Korean People's Army vowing to cancel the 1953 cease-fire that ended the Korean War as well as boasting of the North's ownership of "lighter and smaller nukes" and its ability to execute "surgical strikes" meant to unify the divided Korean Peninsula, at Kim Il Sung Square in Pyongyang, North Korea, on Thursday, March 7, 2013. North Korea on Thursday vowed to launch a pre-emptive nuclear strike against the United States, amplifying its threatening rhetoric hours ahead of a vote by U.N. diplomats on whether to level new sanctions against Pyongyang for its recent nuclear test. The billboard in background depicts a large bayonet pointing at U.S. army soldiers with writing reading "If you dare invade, only death will be waiting for you!" (AP Photo/Jon Chol Jin)

North Koreans attend a rally in support of a statement given on Tuesday by a spokesman for the Supreme Command of the Korean People's Army vowing to cancel the 1953 cease-fire that ended the Korean War as well as boasting of the North's ownership of "lighter and smaller nukes" and its ability to execute "surgical strikes" meant to unify the divided Korean Peninsula, at Kim Il Sung Square in Pyongyang, North Korea, on Thursday, March 7, 2013. North Korea on Thursday vowed to launch a pre-emptive nuclear strike against the United States, amplifying its threatening rhetoric hours ahead of a vote by U.N. diplomats on whether to level new sanctions against Pyongyang for its recent nuclear test. (AP Photo/Jon Chol Jin)

Russia’s UN Ambassador Vitaly Churkin, center, current president for the U.N. Security Council, listens as he confers with China's UN Ambassador Li Baodong, left, before leading council members on a vote for tough new sanctions against North Korea for its latest nuclear test, during a meeting at U.N. headquarters Thursday, March 7, 2013. The unanimous vote by the U.N.'s most powerful body sparked a furious Pyongyang to threaten a nuclear strike against the United States. (AP Photo/Bebeto Matthews)