(Adds fresh quotes from U.S. envoy Hill) By Linda Sieg TOKYO, June 19 (Reuters) - North Korea should move quickly to shut down its source of bomb-grade plutonium, a top U.S. envoy said on Tuesday, voicing hope that stalled six-party talks on scrapping its nuclear arms programme could resume next month. But shortly after Assistant Secretary of State Christopher Hill arrived in Tokyo for talks with his Japanese counterpart, Japan's NHK television said North Korea had fired a non-ballistic, short-range missile towards the Sea of Japan earlier in the day. Hill declined comment on the report, but South Korea's Yonhap news agency quoted an intelligence source as saying the missile was short range and probably part of a military drill. Japanese Chief Cabinet Secretary Yasuhisa Shiozaki declined either to confirm or deny reports of the missile launch, but told reporters: "I don't think we're currently in a situation where Japan's national security has been significantly affected." Hill, speaking after talks with Japanese nuclear envoy Kenichiro Sasae, sounded cautiously optimistic that six-way talks among the two Koreas, the United States, China, Russia and Japan would resume. "Obviously, we look foward to convening the talks at a very early date, probably in July," Hill told reporters. "I would like it sooner rather than later." Hill said that North Korea appeared to have received the funds it had demanded be released from a frozen bank account in Macau as a condition for closing its only nuclear reactor, the source of its weapons-grade plutonium. North Korea said on Saturday it would allow U.N. nuclear inspectors into the country as part of a disarmament deal after nearly $25 million in funds Washington had blocked for nearly two years started to make its way back to the impoverished country. IAEA VISIT The International Atomic Energy Agency (IAEA) plans to send a senior delegation to North Korea next week to agree details for a return of its inspectors to monitor the reactor shutdown, agreed to under Pyongyang's Feb. 13 deal with regional powers. "We want the IAEA to be able to quickly make an agreement and get on with shutting down the reactor," Hill told reporters in Seoul, where he met South Korean officials. China, chief backer of the reclusive state, praised North Korea for its latest move. "We also hope that all the concerned parties will continue taking positive steps, will conscientiously abide by their commitments and take actions in a comprehensive and balanced way," Chinese Foreign Ministry spokesman Qin Gang told a news conference in Beijing. An unidentified North Korean diplomatic source, quoted by Russia's Interfax news agency on Monday, said North Korea planned to seal the reactor at Yongbyon, about 100 km (60 miles) north of Pyongyang, in the second half of July. Pyongyang, which tested its first nuclear device last October, is widely believed to have already produced enough material to make several weapons. TWO-MONTH DELAY Hill has said that despite more than two months of delay in starting to dismantle the North's atom bomb programme, it would still be possible to complete the nuclear disarmament of the communist state by the end of the year. The North missed a mid-April deadline to shut its Soviet-era reactor agreed to under the Feb. 13 deal because of the row over its funds, blocked over allegations of North Korean involvement in dollar counterfeiting and other illicit activity. If Pyongyang now keeps its part of the deal and shuts down its nuclear facilities, the United States is likely to provide the economically struggling state with $2 million worth of emergency humanitarian aid, Japan's Mainichi newspaper reported. Analysts had said Hill was likely to urge Japan to ease its tough stance toward North Korea in a feud over citizens kidnapped decades ago so that it can help provide energy aid to the North. That shift, though, would be tough for Prime Minister Shinzo Abe ahead of a national election expected in July. In public, Hill stressed that the abduction issue -- a highly emotive one for many Japanese -- was also vital to Washington, but added that progress on denuclearisation could help build a base for progress on the kidnappings. Separately, Philippine Foreign Secretary Alberto Romulo left Beijing for Pyongyang to meet North Korea's number two leader, Kim Yong-nam, and newly appointed Foreign Minister Pak Ui-chun. Romulo told Reuters ahead of his visit that he would invite Pak to the ASEAN Regional Forum (ARF) in Manila on Aug. 2. ARF is the Asia-Pacific's main security grouping. In addition to the 10 members of the Association of Southeast Asian Nations, it brings together other countries, including all of the six-party talks participants. (Additional reporting by Chris Buckley and Benjamin Kang Lim in Beijing, Jon Herskovitz in Seoul, and George Nishiyama and Sieg, Chisa Fujioka and George Nishiyama in Tokyo)
