A team of US officials and nuclear experts crossed the border into North Korea today on a rare visit to survey the communist state's nuclear facilities.
They will be joined by experts from Russia and China at the invitation of Pyongyang in what Washington has called another key step towards finally ridding the Korean peninsula of atomic weapons.
Speaking last night, the head of the US delegation, Sung Kim of the State Department, said the inspections "should set the stage for the next phase of disabling".
North Korea has agreed to fully account for and disable its nuclear weapons programme by the end of this year under a February deal with South Korea, the United States, Japan, Russia and China.
It has let in international nuclear inspectors and shut down its main Yongbyon nuclear complex, which had produced bomb-grade plutonium, in return for 50,000 tonnes of heavy fuel oil.
By completing full disarmament, the impoverished North will receive an additional 950,000 tonnes of oil or other aid of same value.
US President George W. Bush has also offered a peace treaty with the North if it gave up its nuclear weapons programme.
North Korea tested its first atomic device a year ago and is thought to have enough fissile material to make several nuclear warheads.