Christopher Hill, the chief U.S. envoy to North Korean nuclear talks, says North Korea should undertake more steps towards denuclearisation after U.N. inspectors verified that it had shut down its Soviet-era Yongbyon nuclear reactor. The reactor, which provides the secretive state with material for arms-grade plutonium, was closed around the time North Korea received the first shipment of over 6,000 tonnes of oil provided by Seoul as part of an aid-for-disarmament deal. The next step will be to verify that North Korea has shut other facilities at Yongbyon, located about 100 km (60 miles) north of Pyongyang. Hill said the reactor closure marked a good beginning. But there was more to be done. In an interview with Reuters, Hill explained he wants Pyongyang to move to disable its nuclear facilities and provide an inventory of its nuclear arms programmes, including one to enrich uranium for weapons. "I would like a situation where, first of all, we get the comprehensive list. And that means all nuclear programmes, that means not just plutonium but we need to get some clarity with what has been going on with uranium enrichment," Hill said. He likened North Korea's nuclear disarmament to "one of those video games where every level becomes more difficult than the previous level". "So I think the most difficult level of this game that we are in is the actual surrender of weapons and abandonment of all this fissile material, that is going to be the tough one. It remains to be seen how we are going to get there," he said. Hill said he wanted "to get going with the task of beginning a peace process that would run parallel to the six-party process." The six-party talks, where North Korea sits down with the United States, South Korea, China, Japan and Russia, are due to resume on Wednesday to map out the next stage of the disarmament process. The five have promised North Korea massive economic aid and better diplomatic ties for scrapping its nuclear arms program. "No one is prepared to deal with North Korea on a normal basis if it continues to hold these nuclear weapons. I mean this is a real test of the non-proliferation treaty. It is the real test of the world order if a country can just go off and build these weapons," Hill said. In 1994, North Korea froze the Yongbyon reactor in exchange for energy aid. In late 2002, the United States accused Pyongyang of violating that deal by having a secret programme to enrich uranium for weapons. In December 2002, North Korea said it was restarting the Yongbyon reactor. It disabled IAEA surveillance devices and expelled their inspectors.