N. Korea back in nuclear building?

North Korea has begun reassembling its main nuclear complex, its only known source of bomb-making plutonium, the South Korean government said Wednesday.

The North announced last week that it had stopped disabling its nuclear facilities and threatened rebuild them, angry that it had not yet been removed from the U.S. list of state sponsors of terrorism. The U.S. maintains the North has not fulfilled the requirements for being removed.

While North Korea has not yet threatened to expel American and international nuclear experts from its facilities in Yongbyon, the country's action threatens to sabotage five years of on-and-off talks between North Korea and the five powers – the United States, China, Russia, Japan and South Korea – seeking to end its nuclear weapons programs.

The North has often delayed and backtracked on commitments as a negotiating tactic, but its latest move complicates President Bush's hopes of cementing major gains in North Korean nuclear disarmament before he leaves office.

On Wednesday, Japan's public broadcaster NHK and the Kyodo News agency reported that North Korea had started reassembling its nuclear facilities on Tuesday. The reports cited unidentified officials related to the disarmament talks.

In a statement from South Korea's Foreign Ministry confirming that the North had begun rebuilding, a spokesman, Moon Tae-young, said: “Our government expresses serious concern because this goes against the movement toward denuclearizing North Korea and damages the six-nation process.”

Bush administration officials were measured in their response to the North Korean action, but said that they were dispatching Christopher Hill, assistant Secretary of State for East Asia, to Beijing for talks.

Since last year, experts from the U.S. and the U.N. nuclear watchdog, the International Atomic Energy Agency, together with North Korean engineers, had been disabling facilities at Yongbyon, to at least temporarily shut down the North's plutonium-based nuclear weapons program. North Korea is suspected of running a separate, clandestine program using enriched uranium.

Work began last year to disable Yongbyon's reactor, a factory that produces fuel for the reactor, and a laboratory that can extract plutonium from spent fuel rods. Eight of 11 disabling tasks had been completed.

One Bush administration official noted that it would be extremely difficult to rebuild Yongbyon now that the cooling tower has been destroyed and the facility has been largely dismantled.