US envoy Christopher Hill arrived Thursday in Pyongyang in an unannounced visit to press North Korea to comply with an agreement to end its nuclear activities, according to dpa. Hill said after arriving that he wanted to lay the groundwork for moving forward on six-nation talks to dismantle North Korea's nuclear programme, China's official Xinhua News Agency reported. "We hope we can make up for some time we lost this spring," the top US negotiator in the nuclear talks said of the discussions that have been stalled for months, adding that he had been invited by North Korea. Hill's two-day visit was the first by a high-ranking US official to North Korea in five years. The US assistant secretary of state for East Asian and Pacific affairs is on a tour of countries involved in the nuclear talks, and on Wednesday in Tokyo, he said he believed the talks involving the two Koreas, the United States, China, Japan and Russia could begin as soon as early July if North Korea begins shuttering its main nuclear reactor as promised. His trip came four days after North Korea invited United Nations nuclear inspectors back into the country to begin the process of shutting down the Yongbyon reactor as required by the February 13 disarmament agreement. The closing of Yongbyon has been delayed for more than two months because of a dispute over funds in a North Korean bank account. The UN's nuclear watchdog, the International Atomic Energy Agency, said a team would travel to Pyongyang next week to work through technical details to shut the plant. South Korea's Foreign Ministry said Hill had left for Pyongyang from South Korea and was expected back on Friday. Seoul expected Hill to meet his North Korean counterpart, Kim Kye Gwan, during his visit. Hill will also meet with North Korean Foreign Minister Pak Ui Chun, US State Department spokesman Sean McCormack said. McCormack said now that the issue of the North Korean funds has been resolved it is time for Pyongyang to live up to its commitments. "We are testing the proposition that North Korea has made that strategic decision to abandon it's nuclear weapons programmes and to abandon its nuclear programme," McCormack said. South Korean and Japanese media reports, citing officials, added that the diplomat would discuss when to resume the six-party negotiations and initial procedures to shut down and seal the Yongbyon reactor. Six nation talks have been stalled because of a delay in transferring 25 million dollars in North Korean funds that had been frozen at a Macau bank under US sanctions. The United States agreed to release the money to nudge along the nuclear talks. But technical and legal problems held up the money transfer, prompting North Korea to refuse meeting an April deadline to close the Yongbyon. The funds have not reached a North Korean account in Russia. South Korean nuclear negotiator Chun Yung Woo said Thursday that he expected informal talks to begin next month as a prelude to a new round of six-nation discussions, the Yonhap News Agency reported. The informal meetings should be held before July 10, he added. Chun called Hill's visit to North Korea "a good sign" for the future of the talks. It followed Washington's years-long refusal to speak to North Korea directly. "The two sides having dialogue is a good thing," he was quoted as saying. "We have to see the North's response for details, however." Hill was expected to return to South Korea and then to Japan to brief officials there on his North Korea meetings before departing Saturday for Washington. This week, Hill also visited Beijing, the host of the six-party talks.