WASHINGTON -- A blunt and explicit threat from North Korea on Thursday that its missile and nuclear programs would "target" the United States poses a stark challenge to the Obama administration even as it hoped it could focus its major diplomatic effort on restraining Iran's less-advanced nuclear program.
The statement from the North Korean National Defense Commission, the country's highest military body, was considerably more specific than past warnings from the country, and explicitly ruled out any talks over "denuclearization" of the Korean Peninsula, which has been the objective of on-again, off-again talks with Pyongyang for two decades.
"We do not hide that a variety of satellites and long-range rockets which will be launched by the DPRK one after another and a nuclear test of higher level," the statement said, "will target against the U.S., the sworn enemy of the Korean people." As in the past, the statement also suggested North Korea viewed its weapons programs as a "deterrence" against attack.
It may prove that the statement was another outburst by an insecure, starving country; North Korea has often threatened to strike the "heart" of the United States, and a popular propaganda poster there shows a missile hitting what looks like Capitol Hill.
But the difference now is that the country has just completed a successful long-range rocket test that showed for the first time that its goal of designing a weapon that could hit the United States could be within reach in the next several years.
In recent weeks American intelligence officials have become concerned that the country's new and untested leader, Kim Jong-un, may have decided that confrontation with the West could prove a more successful strategy to retaining power than a new attempt at economic reform. Instead, he appears to be following in the path of his grandfather and his father, both of whom pressed for greater nuclear and missile capability.
The White House responded to the North Korean declaration by saying it was "needlessly provocative." Jay Carney, the White House press secretary, told reporters that "further provocations would only increase Pyongyang's isolation," a variant of the line the White House has used every time the North has issued a threat, launched a missile or revealed a new nuclear facility.
But deeper isolation does not appear to be the young Mr. Kim's greatest fear. Until now, China, which supplies the North's energy and some of its food, has not cut off its aid in response to North Korean actions. Chinese officials have made it clear, in meetings with their American counterparts, that they fear instability in North Korea more than they worry about the country advancing its longstanding nuclear and missile capabilities.
"If you look back over the past four years," one former administration official said recently, "we haven't moved the Chinese at all."
It is hard to know what exactly the North Korean meant by its statement that the nuclear test would be of a different nature. It could indicate that the country will try to show that it can manufacture a warhead small enough to fit on a missile, though that technology is extremely difficult.
It could also mean that it plans to try to test a uranium weapon, created from a new uranium-enrichment program that it showed two years ago to a visiting American scientist. The North's two previous nuclear tests, in 2006 and 2009, used some of its limited stockpile of plutonium.
But there is little question that the North is making preparations at the Punggye test site in the country's northeast, near the Chinese border for a possible nuclear test. Col. Wi Yong-seob of the army, deputy spokesman of the Defense Ministry of South Korea, said on Thursday, "North Korea can conduct a nuclear test as soon as its leadership makes up its mind."
North Korea had previously hinted at the possibility of conducting a nuclear test, as its Foreign Ministry did on Wednesday when it issued a scathing statement rejecting a unanimous resolution that the United Nations Security Council adopted on Tuesday. The resolution tightened sanctions and condemned North Korea's Dec. 12 rocket launching as a violation of earlier resolutions that banned the country from conducting any tests involving ballistic-missile technology.
North Korea has since declared that it would shun any talk on denuclearizing the Korean Peninsula, adding that it would not give up its nuclear weapons until "the denuclearization of the world is realized."
The North's statement on Thursday indicated that Mr. Kim, despite recent hints of modest economic changes and openness in North Korea, was likely to follow the pattern his father established when he ran the country: a cycle of a rocket launching, United Nations condemnation, and nuclear testing.
"It's a major test for Kim Jong-un," said Koh Yu-hwan, a North Korea specialist at Dongguk University in Seoul. "Unlike the rocket launching in December, which the North has said was conducted because it was his father's dying wish, a nuclear test will be Kim Jong-un's decision, one for which he will be held responsible."
A nuclear test would compel the United States and South Korea to take a tough stance, dispelling hopes that Mr. Kim might use the inaugurations of new governments in those two countries to open a new path of engagement.
Glyn Davies, Washington's special envoy on North Korea, warned on Thursday that a nuclear test would be "a mistake and a missed opportunity" for North Korea.
"This is not a moment to increase tensions on the Korean Peninsula," said Mr. Davies, who was visiting Seoul to coordinate the North Korea policies of President Obama's second-term administration and the government of President-elect Park Geun-hye in Seoul. From Seoul, Mr. Davies will move on to Beijing and then to Tokyo to continue policy consultations with the new governments there.
President Lee Myung-bak, who will hand over the South Korean presidency to Ms. Park next month, said on Thursday that his "biggest worry" was that North Korea might launch a military provocation timed to the governmental transition in Seoul.
On Thursday, the North expressed bitterness at China and Russia's endorsement of the United Nations resolution, denouncing "those big countries" as "failing to come to their senses." It said that North Korea's drive to rebuild its moribund economy and its rocket program, until now billed as a peaceful space project, will now "all orientate toward the purpose of winning in the all-out action for foiling the U.S. and all other hostile forces' maneuvers."
"They are making a brigandish assertion that what they launched were satellites but what other country launched was a long-range missile," the statement said, insisting that North Korea had a sovereign right to test rockets.
Moon Soon-bo, an analyst at the private Sejong Institute, said North Korea's harsh reaction reflected the economic pain the isolated government was anticipating as a result of the new resolution, which expanded the number of ways that countries can interdict and inspect cargo bound for the North.
North Korea said the Unha-3 rocket it launched in December put a scientific satellite into orbit. But Washington said the launching was a cover for testing technology for intercontinental ballistic missiles. After analyzing the debris of the rocket North Korea fired, South Korean officials said North Korea indigenously built crucial components of a missile that can fly more than 6,200 miles.
Analysts speculated on Thursday that North Korea might test launch one of its KN-08 missiles. KN-08, first unveiled during a military parade in the North Korean capital, Pyongyang, in April last year, is the North's biggest missile yet but has never been flight tested, according to officials in Seoul.
This article originally appeared in The New York Times.