SEOUL – A team of inspectors from America, China and Russia headed Wednesday to North Korea’s main nuclear facilities to study how to permanently disable them so that the communist country can no longer produce atomic bombs.

The delegates arrived yesterday in the North Korean capital, Pyongyang, ahead of their inspection tour 60 miles north in Yongbyon to determine how to disable facilities there under a February international accord.

Their findings will be reported to chief delegates at six-nation nuclear talks, which are expected to convene later this month to finalize a timeline for further steps in the North’s nuclear disarmament.

American State Department official Sung Kim told reporters in Pyongyang that it was not yet certain which of the North Korean facilities would be inspected, adding that the team would possibly return tomorrow to Pyongyang, broadcaster APTN reported.

The North in July shut down its sole operating reactor at Yongbyon, which produced plutonium for bombs and is being monitored by the International Atomic Energy Agency. The Yongbyon site also includes facilities for reprocessing nuclear fuel from the reactor. North Korea also has long-dormant construction sites nearby for two larger reactors.

American and North Korean nuclear envoys agreed in talks earlier this month in Geneva that Pyongyang’s nuclear facilities would be disabled by year-end — meaning that they could not be easily restarted to continue making material for bombs. Future negotiations will determine how to dismantle the facilities.

The top American envoy to South Korea reaffirmed today that Washington hoped to complete the disablement of the North’s nuclear facilities in 2007.

American Ambassador Alexander Vershbow told South Korea’s YTN news channel that contacts between the North and the countries at the arms talks “give us at least a reasonable degree of confidence that the current phase can be completed successfully by the end of this year.”

After years of delays on disarmament since the latest nuclear standoff began in 2002, the North has recently displayed an unprecedented willingness to scale back its nuclear program in exchange for political and economic concessions at arms talks that also include China, Japan, Russia, South Korea and America.

However, the North has yet to commit to giving up the nuclear bombs it is believed to have already built — as many as a dozen or more. North Korea conducted a test detonation of a bomb in October, confirming it could make atomic weapons.

Mr. Vershbow acknowledged taking that further step would not be easy and said that America would seek to address the North’s weapons next year. “The big challenge, actually getting rid of nuclear weapons and eliminating the nuclear programs, still lies ahead,” he said.