During a visit to North Korea this week, China's top nuclear envoy, Vice Foreign Minister Wu Dawei, held talks with senior officials and saw first-hand the disablement of the plutonium-producing facility at Yongbyon.

"The DPRK (North Korea) told Vice Foreign Minister Wu that it would seriously honour its commitments and implement its obligations," foreign ministry spokesman Qin Gang said in regards to a six-nation disarmament pact.

Qin, however, stopped short of saying whether Pyongyang had specifically promised to meet a December 31 deadline to declare and disable all of its nuclear programmes, as agreed in the pact.

Qin gave a cautiously positive assessment at the work going on at Yongbyon, after Wu visited it on Tuesday.

"The disablement of nuclear facilities at Yongbyon... is an important part of the denuclearisation plan of the Korean Peninsula. Relevant work is proceeding smoothly in accordance with the agreements reached in six-party talks," Qin said.

The pact would see Pyongyang disable Yongbyon facility and declare all its nuclear programmes by December 31, in return for energy aid and the promise of future major diplomatic concessions.

But the process has reportedly hit a key problem -- the North's refusal to address its suspected highly enriched uranium weapons programme to the satisfaction of the United States.

US President George W. Bush this month wrote to North Korean leader Kim Jong-Il, urging him to fully disclose his nuclear programmes.

The six-party talks group the two Koreas, host China, the United States, Russia and Japan.