North Korea has slowed disablement work at its key nuclear reactor to a snail's pace, complaining of a delay in delivery of energy aid it is supposed to receive, Japan's Kyodo news agency quoted diplomatic sources as saying, Reuters reported.
North Korea resumed disablement of the reactor after the United States took the reclusive nation off its terrorism blacklist in October following an agreement between the countries on a series of measures to verify Pyongyang's nuclear programme.
Under a 2005 six-nation agreement, North Korea agreed to abandon its nuclear programmes in exchange for economic and diplomatic incentives.
The agreement had appeared in danger of collapse earlier this year when North Korea began to reverse the disablement of its Soviet-era nuclear reactor at Yongbyon.
Kyodo quoted the unidentified sources as saying the number of nuclear fuel rods that are pulled from the reactor and put into an adjacent water pond at the Yongbyon nuclear complex has gone down to 15 a day from last month's 30 a day.
North Korea made the changes at the complex, about 90 kilometers (56 miles) from the capital Pyongyang, about a week ago because shipments of energy aid were slow in coming, the news agency quoted the sources as saying.
Under an agreement last year between North Korea and its five negotiating partners, up to 1 million tonnes of heavy fuel, or energy aid equivalent to that, will be provided to North Korea when it disables its nuclear facility at Yongbyon and declares its nuclear programmes.
But Japan, one of the five nations, has so far refused to give energy aid to North Korea because of a dispute over abducted Japanese citizens.
Tokyo is under pressure from Seoul, which wants Japan to join South Korea, China, Russia and the United States in providing promised energy aid.
U.S. Assistant Secretary of State Christopher Hill has said
countries outside the five-nation group negotiating North Korea's nuclear disarmament have volunteered to help supply Pyongyang with energy as a reward.
Kyodo also quoted a separate source close to the six-party talks as saying North Korea is likely to speed up work once countries clarify the schedule for the energy assistance at the next denuclearisation talks, expected to be held some time in the near future.