The comments were made by North Korea's lead official after formal discussions in China on the North's nuclear weapons program. North Korean delegate Ri Gun told U.S. Assistant Secretary of State James Kelly that whether Pyongyang tests, exports or uses its bombs depends on U.S. actions.
Kelly did not respond to Ri's comment, said the U.S. official. Kelly was to fly to Seoul on Friday to meet with South Korean officials.
According to the U.S. official, Ri said during the plenary session earlier that North Korea has reprocessed all 8,000 spent nuclear fuel rods in its possession.
If true, that would put North Korea much closer to building six to eight additional weapons beyond the one or two it is believed to have at present.
The U.S. official said CIA assessments indicate that reprocessing has not yet started. The discrepancy, the official said, suggests the either Ri is lying or the United States has suffered a major intelligence failure.
The formal talks in China ended with State Department officials saying it was uncertain whether discussions on Pyongyang's nuclear program would continue. The officials denied reports the talks had broken down.
Earlier, Secretary of State Colin Powell told a gathering of experts from the Asia-Pacific region that the talks, involving the United States, North Korea and China, had concluded, leaving the impression there would not be a third day of discussions on Friday.
Powell expressed hope that South Korea and Japan would be able to participate "when and if" there is another round of talks.
He added: "North Korea should not leave the meetings having the slightest impression that they might force us to make a concession we would not otherwise make."
The U.S. Embassy and Chinese Foreign Ministry said they had no details of Thursday's discussions. But ministry spokesman Liu Jianchao said the talks were "conducive to mutual understanding and finding ways to resolve the North Korean nuclear question peacefully."
Before the start of the second day's meeting in Beijing, North Korea accused the United States of leading the region toward war, an apparent attempt by the communist nation to increase pressure on negotiators, according to the U.S. officials.
"The situation on the Korean Peninsula is so tense that a war may break out any moment due to the U.S. moves," the North's KCNA news agency.
The North's Korea People's Army vowed to "put all people under arms and turn the whole country into a fortress" and urged its soldiers to become "human bombs and fighters ready to blow up themselves" to protect leader Kim Jong Il.
Washington says the North revealed during a visit by Kelly to Pyongyang in October that it was trying to develop nuclear weapons in violation of a 1994 pledge. The North has disputed the U.S. claim.
Since the latest nuclear tensions erupted, Pyongyang has become the first country to withdraw from the nuclear Non-Proliferation Treaty and restarted a plutonium-producing reactor.
North Korea is believed to want economic aid in exchange for concessions. Its leaders are outraged over U.S. moves to cut off oil shipments because of its suspected nuclear weapons program, and fears it is next on Washington's list for military action.
It said relations with the United States had hit "rock bottom" because President Bush named North Korea as part of an "axis of evil," along with Iran and Iraq.
KCNA said the war in Iraq had shown the only way for a country to protect itself was to have a strong military deterrent. Officials from Seoul and Washington say the swift U.S.-led victory in Iraq prompted North Korea to agree to the nuclear talks.
The United States hopes eventually to include Japan and South Korea in the talks. Kelly briefed South Korean and Japanese diplomats in Beijing following Wednesday's discussions, the U.S. Embassy said. He is scheduled to visit Seoul for meetings immediately after the Beijing talks.
South Korea and North Korea plan, separate, Cabinet-level talks this week.
The three-way talks in Beijing represent a compromise between approaches favored by the United States and North Korea. Pyongyang wanted bilateral talks with Washington, but the Bush administration insisted on regional discussions.