Since November, US experts have been on the ground at Yongbyon overseeing disablement of the reactor.
The US state department says eight-out-of-11 agreed disablement activities at three core facilities on the complex have been completed and that more than one-third of spent fuel rods have now been discharged.
The main sticking point in the declaration has been Pyongyang’s reluctance to discuss any transfer of nuclear technology to other countries, notably Syria, as well as its suspected pursuit of uranium enrichment.
George Bush, the US president, said in late April that he released intelligence about the suspected North Korea-Syria nuclear collusion to put pressure on Pyongyang to come clean on all its nuclear activities.
Pyongyang denies both charges of uranium enrichment and technology proliferation.
Under a reported deal, it will merely “acknowledge” US concerns about the two issues in a confidential separate document to Washington.