Radioactive contamination could delay the work of experts from the UN nuclear watchdog to seal North Korea's nuclear facilities, shut down by Pyongyang under a disarmament deal agreed in Beijing in February, the Kyodo news agency said Wednesday.

Another group of inspectors from UN's nuclear watchdog has arrived in North Korea to observe the second phase of Pyongyang's obligation to wrap up its controversial nuclear program, the Xinhua news agency reported Saturday.

The U.S. envoy to the six-party talks on North Korea's nuclear program says completing the next phase of the disarmament process is still feasible by year's end, even though talks in Beijing last week failed to produce a timetable for it. Assistant Secretary of State for East Asian Affairs Christopher Hill says envoys will convene again on the issue by early September.

South Korea is expected to complete a fuel oil shipment to the North on Sunday as part of a six-nation deal to encourage Pyongyang's nuclear disarmament, a Seoul-based news agency said.

North Korea's nuclear negotiator says Pyongyang should receive light-water reactors to generate power in exchange for disabling its Yongbyon nuclear facilities.

Six-party talks on North Korea's nuclear disarmament ended Friday without setting a deadline for the next steps in preventing the North from developing nuclear weapons, but participants reaffirmed their commitment to push forward with the process.

Experts from the UN nuclear watchdog will install monitoring equipment at five North Korean nuclear facilities in the next few weeks as part of an international effort to fold Pyongyang's nuclear program, a Russian diplomat said.

Russia's envoy to the current negotiations on North Korea's nuclear program in Beijing said Pyongyang promised to declare and deactivate all its nuclear facilities as another step toward complete nuclear disarmament.

Talks on North Korea's nuclear disarmament are to be extended by one day through Friday, the Japanese delegation to the talks said Thursday. The talks, which also include China, Russia, the U.S. and the two Koreas, began Wednesday in Beijing and was originally planned for two days through Thursday.

North Korea reaffirmed its commitment to nuclear disarmament at six-nation talks on its nuclear program, which resumed in Beijing Wednesday, a Russian diplomat said.

The chief U.S. nuclear envoy expressed optimism after a day of meetings with his North Korean counterpart Tuesday, saying no new obstacles emerged to progress on disarmament following Pyongyang's shutdown of its sole operating reactor.

Moscow welcomed as "positive" North Korea's claim that it has shut down a nuclear reactor at the heart of international efforts to curb Pyongyang's atomic program, while U.S. officials offered cautiously hopeful appraisals.