North Korea threatened the United States with a preemptive nuclear strike, raising the level of rhetoric just before the UN Security Council approved new sanctions against the reclusive country.
US Ambassador to the United Nations Susan Rice said North Korea's threats would achieve nothing and would only further isolate the country.
China's UN Ambassador Li Baodong said Beijing wanted to see "full implementation" of the new UN Security Council resolution that tightens financial restrictions on Pyongyang and cracks down on its attempts to ship and receive banned cargo.
North Korea has accused the United States of using military drills in South Korea as a launch pad for a nuclear war and has scrapped the armistice with Washington that ended hostilities in the 1950-53 Korean War.
A North Korean general said on Tuesday that Pyongyang was scrapping the armistice. But the two sides remain technically at war as the civil war did not end with a treaty.
North Korea threatens the United States and its "puppet," South Korea, on an almost daily basis.
"Since the United States is about to ignite a nuclear war, we will be exercising our right to preemptive nuclear attack against the headquarters of the aggressor in order to protect our supreme interest," the North's foreign ministry spokesman said in a statement carried by the official KCNA news agency.
North Korea conducted a third nuclear test on February 12, in defiance of UN resolutions, and declared it had achieved progress in securing a functioning atomic arsenal. It is widely believed that the North does not have the capacity for a nuclear strike against the United States mainland.
With tensions high on the Korean peninsula, the UN Security Council voted unanimously to expand its sanctions on North Korea. The new sanctions were agreed after three weeks of negotiations between the United States and China, which has a history of resisting tough measures against its ally and neighbor.
The resolution specifies some luxury items North Korea's elite is not allowed to import, such as yachts, racing cars, luxury automobiles and certain types of jewelry. This is intended to close a loophole that had allowed countries to decide for themselves what constitutes a luxury good.
"These sanctions will bite and bite hard," said Rice.
The export of luxury goods to North Korea has been prohibited since 2006, though diplomats and analysts said the enforcement of UN sanctions has been uneven.
UN Secretary-General Ban Ki-moon, a former South Korean foreign minister, welcomed the council's move, saying in a statement that the resolution "sent an unequivocal message to (North Korea) that the international community will not tolerate its pursuit of nuclear weapons."
The success of the new measures, council diplomats said, will depend to a large extent on the willingness of China to enforce them more strictly than it has in the past.
Pyongyang was hit with UN sanctions in retaliation for its 2006 and 2009 nuclear tests. Those measures were subsequently tightened and expanded after several rocket launches by the North.
In addition to the luxury goods ban, there is an arms embargo on North Korea, and it is forbidden from trading in nuclear and missile technology.
George Lopez, a professor at the University of Notre Dame in Indiana and a former member of the UN panel that monitors North Korea sanctions compliance, said the new measures should have a real impact on North Korea's movement of money and constrain access to equipment for its nuclear and missile programs.
"Now, we may yet see another launch or a bomb test, but over the medium term this resolution will degrade DPRK capabilities to grow its program," Lopez said, using the acronym for the Democratic People's Republic of Korea.
Threats and war games
North Korea's threats were the latest in an escalating war of words by both sides across the armed Korean border this week.
The North's unnamed foreign ministry spokesman said it would be entitled to take military action as of March 11 when US-South Korea military drills move into a full-scale phase.
"North Korea will achieve nothing by continued threats and provocations. These will only further isolate the country and its people and undermine international efforts to promote peace and stability in northeast Asia," Rice told reporters.
President Barack Obama's administration said it had reassured South Korea and Japan "at the highest levels" of its commitment to deterrence, through the US nuclear umbrella and missile defense, in the face of the new threats.
Glyn Davies, the State Department's point man for North Korea, also said in testimony prepared for a Senate hearing that Washington will not accept North Korea as a nuclear state.
Russia's UN Ambassador Vitaly Churkin called for restraint and an end to the threats. "Let's keep our minds cool and keep focused on the need for the only possible rational course of action, and that is returning to six-party talks," he said.
North Korea, which held a mass military rally in Pyongyang on Thursday in support of its recent threats, has protested against the UN censures of its rocket launches. It says they are part of a peaceful space program and that the criticism is an exercise of double standards by the United States.
The North's shrill rhetoric, however, rarely goes beyond just that. Its last armed aggression against the South in 2010 came unannounced, bombing a South Korean island and killing two civilians. It was also accused of sinking a South Korean navy ship earlier in the year, killing 46 sailors.
North Korea was conducting a series of military drills and getting ready for state-wide war practice of an unusual scale, South Korea's defense ministry said earlier.
South Korea and the United States, which are conducting annual military drills until the end of April, are watching the North's activities for signs that they might turn from an exercise to an actual attack, said South Korea's defense ministry spokesman Kim Min-seok.
Kim declined to confirm news reports that the North has imposed no-fly zones off its coasts in a possible move to fire missiles, but he said any flight ban limited to near the coast would not be for weapons with meaningful ranges.
South Korea's military said in a rare warning on Wednesday that it would strike back at the North and target its leadership if Pyongyang launched an attack.