The UN atomic watchdog has said North Korea's move to activate nuclear facilities is "very worrying." The Vienna-based UN inspection agency - the International Atomic Energy Agency - said North Korea had moved 1,000 fresh fuel rods to a nuclear reactor that produces plutonium used in nuclear warheads.
"The big worry (is) if they start to operate the reprocessing plant that will produce plutonium, which can be directly used to manufacture nuclear weapons -- and there again we have no way to verify the nature of the activity," IAEA chief Mohamed ElBaradei told CNN from Sri Lanka on Thursday.
"So the situation is very worrying," he said.
IAEA spokesman Mark Gwozdecky told the BBC the 1,000 fresh fuel rods moved to the reactor site had not yet been loaded into the reactor core. He said they would need to move another 7,000 rods to reach the capacity of the reactor core.
"When we do not have our safeguards in place we're simply not in a position to know whether this material is being used for nuclear weapons or not," Gwozdecky said.
South Korea's President Kim Dae-jung told his security and foreign policy ministers they should seek dialogue with the North through existing channels while working with the United States, Japan and others to defuse the crisis over the facilities closed since 1994.
"South Korea must play a leading role in solving the North's nuclear issue, which is a critical problem for the Korean peninsula," he said, in remarks relayed by his office after the special strategy meeting.
Kim, who favours constructive engagement with the North over the current US approach of playing hard ball, did not spell out specific new measures but his government has opened channels of communication while discussing aid and reunification.
Gwozdecky said earlier North Korean technicians had broken most seals and disabled UN surveillance devices at all four nuclear facilities at Yongbyon, 90 km (55 miles) north of the capital Pyongyang. Cameras had been monitoring a 1994 oil-for-compliance deal that ended an earlier crisis over the North's nuclear ambitions.
South Korean Defence Minister Lee Jun said the North had made no unusual military moves during the dispute. Unification Minister Jeong Se-hyun, echoing a Bush administration official, said its nuclear moves appeared largely aimed at forcing the United States to talk.
But a US official, who accused the North of playing games to draw the United States into talks on normalising relations, said Washington was unwilling to play the game and predicted diplomatic pressure would be enough to bring the North into line.
The latest crisis erupted after the United States said in October the North had admitted operating a secret nuclear weapons programme using highly enriched uranium. The United States, South Korea and other states suspended the oil shipments in December.
The Bush administration, which has labelled the North a member of an "axis of evil" with Iraq and Iran, says it appears to be pacing its provocations to draw a US response.
"It's like a strip-tease," said the administration official, who asked not to be named.
The North insists it has a right to possess nuclear weapons and says Washington must sign a non-aggression pact as a basis for talks on their differences.