A foreign ministry statement said North Korea had "done what it should do" under the deal, according to the official Korean Central News Agency.

Pyongyang should have completed the disablement of its nuclear plants and handed over a complete declaration of all its nuclear programmes and material by December 31, but missed the deadline.

The United States, Japan and South Korea have said they were disappointed the deadline had been missed, although the US State Department said a full and accurate declaration was more important than one delivered on time.

However, the North's foreign ministry said late Friday it had "worked out a report on the nuclear declaration in November last year and notified the US side of its contents."

It said the disablement of North Korea's nuclear facilities had begun in November last year and the unloading of spent fuel rods was scheduled to be completed in about 100 days.

"However, the delivery of heavy fuel oil and energy-related equipment and materials to the DPRK (North Korea), commitments of other participating nations, has not been done even 50 percent," the statement said.

"Now that other participating nations delay the fulfillment of their commitments, the DPRK is compelled to adjust the tempo of the disablement of some nuclear facilities on the principle of 'action for action'."

North Korea agreed last February to give up its nuclear weapons programmes in return for one million tonnes of fuel oil or equivalent energy aid, diplomatic benefits and security guarantees.