Two months ago, North Korea stopped disabling the Yongbyon nuclear facility in anger over U.S. demands that Pyongyang accept a plan to verify its accounting of nuclear programs as a condition for removal from a blacklist of countries accused of sponsoring terrorism.
Until late last week, the North had threatened to reactivate the plutonium reprocessing plant at Yongbyon.
But the North and the U.S. reached a compromise on the verification row following a trip to Pyongyang by chief U.S. nuclear envoy Christopher Hill. Washington announced North Korea's removal from the terror list Saturday, saying Pyongyang had agreed to all its nuclear inspection demands.
U.S. State Department spokesman Sean McCormack said Tuesday he believed the North Koreans had taken steps in the right direction.
"I think, as simply put, the North Koreans have started the reversal of their reversal," he said. "Our monitors are on the ground. And I didn't check this morning to see if they actually were engaged in activities, but I believe that they are free to do so."
Pyongyang had earlier told the International Atomic Energy Agency it would restart work to disable the Yongbyon nuclear reactor and allow international inspectors to resume their activity. The plans were outlined in a restricted document to the agency's 35 board members obtained by The Associated Press.
North Korea also said Sunday it would restart work to disable Yongbyon, though it did not specify a date.
U.N. Secretary-General Ban Ki-moon welcomed the resolution of the dispute. His spokeswoman, Michelle Montas, said Ban considered it "another step towards a verifiable non-nuclear Korean Peninsula."
China also hailed the progress and pledged to move the process forward as host of the nuclear disarmament talks that involve Japan, the two Koreas, the United States and Russia.
"Promoting the six-party talks process serves the common interests of the involved parties," Foreign Ministry spokesman Qin Gang said in a statement issued late Monday. "China appreciates the constructive efforts made by the concerned parties."
Meanwhile, Japan reiterated its demand that Pyongyang resolve the issue of abductions of its citizens by North Korean agents in the 1970s and 1980s, saying it was a precondition for Tokyo's participation in providing aid to the North.
"We will not join the economic and energy aid under the six-party talks unless issues over Japan-North Korea relations, including the abduction problem, are cleared," Prime Minister Taro Aso told an upper house committee Tuesday.
On Tuesday, North Korea's Foreign Minister Pak Ui Chun left for Russia, Pyongyang's Korean Central News Agency said, without elaborating.
Moscow's Foreign Ministry spokesman Andrei Nesterenko said Pak and Russian Foreign Minister Sergei Lavrov would be discussing the status of the six-nation nuclear talks.
North Korea alarmed the world in 2006 by setting off a test nuclear blast. It then agreed to dismantle its nuclear program in exchange for energy aid and other concessions.
The regime began disabling Yongbyon in November, and blew up a cooling tower in June in a dramatic display of its determination to carry out the process. Just steps away from completing the second phase of the three-part process, Pyongyang abruptly reversed course and stopped disabling the plant, until this week.
Associated Press Writer George Jahn in Vienna, Austria, Hyung-jin Kim in Seoul, Gillian Wong in Beijing and Shino Yuasa in Tokyo contributed to this report.