TOKYO — World leaders lashed out at North Korea's vow Tuesday to test a nuclear bomb sometime "in the future," but offered no clear plan for dealing with aggravated tensions over the dictatorship's nuclear weapons ambitions.
U.S. intelligence officials said they had been monitoring recent movement of people and vehicles around at least one suspected test site. But because North Korea has never conducted a nuclear test, it is difficult for intelligence agencies to determine how close the regime may be to setting off a bomb.
The North Koreans did not elaborate on when a test would occur or whether it would be conducted below ground, which experts say is most likely, or in the atmosphere.
Showcasing a nuclear capability would almost certainly deepen North Korea's diplomatic and economic isolation, and could escalate the military buildup in northeast Asia, where grievances run deep and suspicions between capitals are high.
North Korea's Foreign Ministry said Tuesday that a test of the nation's nuclear capability was a necessary response to Washington's financial squeeze on the country, which it described as a "de facto declaration of war." In recent months, Washington has accused Kim Jong Il's regime of counterfeiting U.S. currency and using foreign banks to launder drug money, and has increased pressure on banks around the world not to handle transactions with Pyongyang's military and political elite.
"The U.S. extreme threat of nuclear war and sanctions and pressure compel [North Korea] to conduct a nuclear test, an essential process for bolstering [our] nuclear deterrent, as a corresponding measure for defense," the North Korean statement said.
Secretary of State Condoleezza Rice, traveling in Egypt, said a test would be "a very provocative act."
In Japan, a country within North Korean missile range and where hostility to Kim's regime is a hallmark of its new hard-line government, Prime Minister Shinzo Abe warned that "Japan and the world would definitely not tolerate a nuclear test."
And the South Korean government, which has been reluctant to take a hard line against its volatile neighbor, expressed concern over the announcement and said President Roh Moo-hyun would visit Beijing on Oct. 13 to discuss it.
But there was no immediate consensus on what measures should be employed to defuse the latest threat.
China, North Korea's neighbor and key economic partner, urged calm and restraint.
In New York, the United Nations Security Council declined to issue a formal admonition, noting that it had passed a tough resolution in July demanding that North Korea end all provocative acts and return to six-party talks aimed at dismantling its nuclear weapons program in return for security guarantees and economic incentives.
That resolution followed North Korea's July test firing of a long-range Taepodong 2 missile and a surprising burst of shorter-range missiles, in defiance of similar warnings.
U.S. Ambassador to the U.N. John R. Bolton said the Security Council would meet today on finding a more effective way to discourage Pyongyang from conducting a nuclear test.
The North Korean move adds complexity to nuclear diplomacy as the Security Council seeks ways to dissuade Iran from continuing its nuclear enrichment activities. Pyongyang's defiance underscores the limited power economic sanctions exert over authoritarian governments prepared to let their civilian populations suffer in order to acquire a nuclear capability.
Kurt Campbell, a former deputy assistant secretary of Defense for Asia and the Pacific, called the Korean peninsula "the land of lousy options" and said the U.S. was limited in what it could do to diplomatically or forcibly prevent a test.
"It is a profound and deep failure for the United States and China if North Korea tests a nuclear weapon," he said.
Defense Secretary Donald H. Rumsfeld, traveling in Nicaragua, suggested that a test by North Korea could lead to the further spread of nuclear technology.
"They are an active proliferator," Rumsfeld said. "And were they to test and were they then to proliferate those technologies, we'd be living with a proliferator and obviously we'd be living in a somewhat different world."
While the Defense secretary expressed concern that a test would increase the possibility of a bomb falling into rogue hands, others warned that a proven North Korean capability could encourage other countries in the region, such as Japan, to push for a nuclear arsenal of their own.
North Korea is estimated to have sufficient plutonium for as many as 13 weapons. By 2008, Pyongyang could have the capability to develop as many a 17 nuclear weapons, according to the Institute for Science and International Security, a nonpartisan Washington group headed by David Albright, who has worked with the International Atomic Energy Agency on nuclear inspections.