There is no evidence to support claims that North Korea has begun rebuilding a nuclear plant, US officials say.
The US state department said the North appeared to be moving equipment out of storage at its Yongbyon plant, but there was no effort to reconstruct it.
Earlier reports from South Korea and Japan had claimed the North was actively rebuilding Yongbyon, breaking an international denuclearisation deal.
Pyongyang had previously warned that it had stopped disabling its facilities.
For years, the North has been locked in discussions over its nuclear ambitions with five other nations - South Korea, the US, China, Russia and Japan.
In June this year, the regime blew up the cooling tower of its Yongbyon facility in a symbolic gesture of its commitment to the process.
But last month Pyongyang was angered by the US refusal to remove it from the list of states that sponsor terrorism, and announced it would halt the disabling process.
On Wednesday reports in Japan, backed up by South Korea's foreign ministry, claimed the North Koreans were actively reconstructing the plant.
But state department spokesman Sean McCormack said it appeared that the North was moving previously stored equipment rather than rebuilding.
He told reporters: "To my knowledge, based on what we know from the folks on the ground, you don't have an effort to reconstruct, reintegrate this equipment back into the Yongbyon facility."
He said Christopher Hill, the lead US negotiator in the six-nation nuclear talks, would leave for Beijing on Thursday.
The claims emerge as the UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), published a report on North Korea.
It said the regime had already removed large quantities of essential nuclear materials from Yongbyon even before it agreed to dismantle the plant.
Experts believe the North's facilities would take a year to restore, and the IAEA's report appears to support that view.
Former UN weapons inspector David Albright says the reactor at Yongbyon is mostly intact.
But he said the regime would need to manufacture hundreds - possibly thousands - of fuel rods and rebuild a cooling tower that was blown up in June to get it fully operational.
He believes the North is unlikely to rebuild the plant, but is instead using the threat as a bargaining chip to gain more concessions from the six-party talks.
In June, North Korea finally submitted a long-delayed account of its nuclear facilities - and was expecting to be removed from the US list almost immediately in return.
But the US said that would not be possible until North Korea agreed to inspections aimed at verifying the details that it had disclosed.