North Korea will begin disabling its nuclear facilities Monday, marking the biggest step the communist country has ever taken to scale back its atomic program, the top US envoy to nuclear armament talks with Pyongyang said. US Assistant Secretary of State Christopher Hill said the US intends to achieve the denuclearization of the Korean peninsula while President George W. Bush is still in power, and that North Korea - one of the world's most isolated countries - appeared to be opening up. "I'd like to see us get through this in the current US administration," Hill told a press conference in Tokyo. "We started this process, and I'd like to see us finish it." The North shut down its sole functioning nuclear reactor at Yongbyon in July, and promised to disable it by year's end in exchange for energy aid and political concessions from other members of talks on its nuclear program: the US, China, Japan, South Korea and Russia. Disabling the reactor at Yongbyon, north of Pyongyang, would mark a further breakthrough in efforts to convince the North to scale back its nuclear program. The country conducted its first-ever nuclear test in October of last year. "By Monday morning, they will begin their work," Hill said, referring to the US team that arrived in Pyongyang on Thursday. "It's a very big day because it's the first time it's actually going to start disabling its nuclear program." To disable the program, the facilities must be stripped sufficiently that it would take at least a year for North Korea to start them up again, Hill said. Footage provided by APTN showed some members of the team driving away from their Pyongyang hotel in a bus to the Yongbyon reactor Saturday. Others, including team leader Sung Kim, waved them off. Hill said the delegation was due to arrive at the Yongbyon site on Sunday. Hill added the US hoped to disable North's uranium enrichment program by Dec. 31, not just its plutonium-production facilities at Yongbyon. "By the end of the year ... we hope to have arrived at an important milestone, where there is a complete disablement of the Yongbyon facilities, a full list of additional facilities for disablement, and that uranium enrichment is also resolved to mutual satisfaction," Hill said. Hill also said the US remained worried over the alleged transfer of nuclear technology and materials from North Korea to countries like Syria. Last month, a news report said Israeli strikes in Syria had targeted a partially built nuclear reactor, made with North Korean help, citing US and foreign officials. Still, North Korea appeared to be opening up through the regional engagement over its nuclear program, Hill said, pointing to a flurry of diplomatic activity by Pyongyang in recent months. The North has opened or restored relations with five countries since July, and senior officials have visited Russia, Southeast Asia, Africa and the Middle East - a rare burst of international activity by one of the world's most isolated nations. "As they participate in the six-party process, I think there is a desire to overcome their isolation," Hill said. He warned, however, the process would be slow. The envoy said US lawyers were working with the North to prepare to remove it from a US list of states sponsoring terrorism, but that Pyongyang ultimately needed to meet requirements stipulated under US law. Taking Pyongyang off the terror list, long a key demand of the North, was one of a series of economic and political concessions offered for the country to disable its nuclear reactor that produces plutonium for bombs.