Failing full disclosure from the Stalinist state, the United States will look to unspecified other options, State Department spokesman Rob McInturff said.

"Right up until the deadline we are still hoping to see full disclosure from the North Koreans," he told AFP.

"If that doesn't happen by midnight (on December 31), we'll reevaluate and look to other options," the spokesman said.

Under a six-nation pact, North Korea is required to disable its main nuclear plants by December 31 and declare all its nuclear programs and weaponry.

Experts have said the US-supervised disablement is going well, but may not be completed by year-end for technical reasons related to the removal of fuel rods used to make potentially weapons-grade uranium.

China, Japan and South Korea have all said that Pyongyang is likely to miss the deadline. US officials have stressed they are ready to wait a short while for a full and complete declaration from North Korea.