Under a six-nation deal agreed in Beijing in February, North Korea agreed to disable and declare all its nuclear programmes in return for energy aid and political concessions.

The North shut down its only functioning reactor at Yongbyon in July, and began disabling it and other facilities under the watch of US experts in November.

On Friday however a separate North Korean editorial, carried in the Minju Joson newspaper, said the country had no option but to slow the disablement work, because the US and other parties had delayed fulfilling their commitments under the disarmament pact.

The comments follow a similar claim from a senior North Korean official last week.

"This shows that it is fully up to the US and related countries whether the goal of denuclearising the Korean peninsula would be attained or not," the paper said.

But there has been no word from North Korea on why it failed to meet the declaration deadline, or when or if it will deliver on those commitments.

The stalemate is expected to top the agenda of US nuclear envoy Christopher Hill, who begins a tour of the main parties involved in the six-nation process this weekend.

Aside from North Korea, the other nations involved in the disarmament plan are South Korea, the US, Russia, China and Japan.

Earlier this week a spokesman for the US state department said Washington would continue to press North Korea to deliver on its disarmament commitments.

"We're going to keep hammering away at it. We're not lowering the bar," said Sean McCormack.

His comments followed a New Year's Day message from North Korea which called on the US to scrap its "hostile" policies towards the Asian nation.