SEOUL - A US envoy confirmed Wednesday that North Korea had begun preparations for a nuclear test as the Stalinist state claimed it had taken a key step towards the manufacture of more atomic bombs.
North Korea is believed to have as many as eight nuclear weapons according to some estimates but has never tested one so far.
US Ambassador to Japan Thomas Schieffer, confirming media speculation from the United States, said that could soon change.
"I believe they have taken some preparatory steps," the newly-appointed envoy was quoted as saying in Tokyo at a meeting with a Japanese ruling coalition leader.
Schieffer is the first US official to go on record as saying that a nuclear test could be in the works, after unnamed officials were quoted in the New York Times last week.
According to satellite and other intelligence data those officials believe Pyongyang is building a reviewing stand and filling in a tunnel, clear pointers to a potential underground nuclear test.
Schieffer believed there was a "high possibility" of a nuclear test, according to a Japanese official.
South Korean officials have been sceptical about the reports that North Korea was preparing a test at Kilju, in northeastern North Korea, where satellite images show the suspected tunnel.
US and South Korean intelligence agencies gave been watching the tunnel since the late 1990s and officials in Seoul said as recently as Wednesday that they had neither detected signs nor received intelligence from the United States that would indicate test preparations.
In a separate development Wednesday, North Korea said that it had completed unloading 8,000 spent fuel rods form its nuclear reactor, a step that would allow it to reprocess enough plutonium for about half a dozen bombs.
North Korea shut down the reactor last month, allowing it to unload the spent fuel and remove it for reprocessing.
"The relevant field of the DPRK (North Korea) has successfully finished the unloading of 8,000 spent fuel rods from the 5MW (megawatt) pilot nuclear plant in the shortest period recently," a foreign ministry spokesman was quoted as saying by the official Korean Central News Agency.
The spokesman added that North Korea "keeps taking necessary measures to bolster its nuclear arsenal for the defensive purpose of coping with the prevailing situation, with a main emphasis on developing the self-reliant nuclear power industry."
The five-megawatt reactor at Yongbyon, 90 kilometers (50 miles) north of the capital Pyongyang, was frozen under a 1994 deal with the United States which collapsed in 2002 following US allegations that Pyongyang was still pursuing nuclear weapons.
The US government believes North Korea already had enough plutonium for one or two crude nuclear devices before the deal collapsed.
Then North Korea claimed in late 2003 that it had reprocessed a first batch of 8,000 spent fuel rods from the five-megawatt reactor that would allow it to produce around six more bombs.
If North Korea reprocesses a second batch of spent fuel it claims to have unloaded, it could double that number of bombs, according to experts.
The spokesman said North Korea had also resumed construction on its 50-megawatt and 200-megawatt nuclear plants in December 2002, blaming Washington for the collapse of the 1994 accord.
The developments further clouded prospects for the resumption of talks to end the nuclear standoff any time soon.
Beijing has hosted three rounds of negotiations also involving the two Koreas, the United States, Japan and Russia aimed at solving the standoff over North Korea's nuclear ambitions.
A fourth round, originally scheduled for September last year, has so far not taken place due Pyongyang's reluctance to return to the negotiating table.
05/11/2005 13:37 GMT