The caution came a day after the South reported the North had milled “a small number” of its spent nuclear fuel rods into weapons-grade plutonium.
The director of South Korea’s National Intelligence Agency, Ko Young-koo, also said the North had conducted about 70 high-explosive tests 25 miles outside of Yongbyon, the heart of the North’s nuclear program. Although the blasts were not directly part of a nuclear test, high-explosives can be used as triggers for nuclear devices.
If accurate, the allegations would support claims that the North is developing nuclear weapons. According to weapons experts, the country’s cache of 8,000 spent fuel rods could be used to produce five or six of the devices.
American officials said Thursday they could not confirm the South Korean report, but added they were monitoring the North’s work.
“Our assessment of where they are on reprocessing is not 100 percent clear. There’s enough question to want to leave ourselves some wiggle room on that,” an unnamed U.S. official told Reuters. “It is something we follow very closely. We are always looking at all information available.”
The latest reports come just days after North Korea issued new dire warnings about the dangers of nuclear war erupting with the United States.
“It is a grim reality that the black clouds of nuclear war are gathering on the Korean Peninsula minute by minute,” the North Korean government said in a statement at the beginning of ministerial-level economic talks with the South.
In April, North Korea said it was reprocessing spent uranium rods, a step necessary to produce weapons-grade plutonium. It later backed away from the claim, saying it was only “going forward to reprocess” the rods.
The U.S. government and others have said multilateral talks among China, North Korea, South Korea, Japan and the United States are the only way to resolve international concern over the North’s nuclear program. China, South Korea and Japan are within range of current North Korean missiles.
Chinese and South Korean officials met this week to consider the continuing crisis. China’s vice foreign minister, Dai Bingguo, will go to Pyongyang in an effort to persuade the North to agree to the multilateral talks.
North Korean officials in the capital Pyongyang reiterated their long-standing demand this week that they would agree only to bilateral talks with the United States.
“We are prepared both for talks if certain foreign forces want dialogue and to go to war if they want war,” North Korean Cabinet official Kim Ryong-song said, referring to the United States. “But if the foreign forces ignore our position or use force, then we will demonstrate our power.”
The North agreed to end its nuclear program and submit its facilities to international inspection, in exchange for aid, under a 1994 agreement with the United States. But the U.S. government has said that North Korea authorities admitted in October 2002 that Pyongyang had a secret nuclear program, a claim that that the North later denied.
Relations between the two nations quickly eroded. Within a month of the State of the Union, North Korea ejected international monitors from the United Nations’ International Atomic Energy Agency and restarted a five-megawatt reactor at Yongbyon.