Now comes the hard part in North Korea talks

BEIJING, July 17 (Reuters) After securing the shutdown of a North Korean nuclear reactor, negotiators gathered in Beijing today with the much harder task of coaxing Pyongyang to give up a trove of atomic secrets long guarded as vital for its survival.

Envoys from six countries sit down to two days of talks on Wednesday after UN nuclear inspectors verified the shutdown of the North's Yongbyon reactor.

The reactor produces material that can be turned into weapons-grade plutonium and in February North Korea agreed to close it in return for 50,000 tonnes of heavy fuel oil, which began moving there from South Korea last week.

North and South Korea, the United States, China, Japan and Russia will now begin to explore how to scrap the Yongbyon complex and terminate North Korea's nuclear weapons potential.

Negotiators warned of turbulent talks ahead. Japan's Kenichiro Sasae welcomed the shutting of Yongbyon but underscored the difficulty of persuading North Korea to disclose covert nuclear activities.

''This is just a first step of their undertaking and I believe very long and difficult issues will be in store for us,'' he told reporters after arriving in Beijing.

South Korean envoy Chun Yung-woo said the talks faced ''a bumpy road''. North Korean chief negotiator Kim Kye-gwan said envoys would shift their attention to the post-shutdown phase.

''So the talks will focus on the sequence of the obligation and actions to be taken by the concerned parties at the second phase under February 13 agreement,'' Kim said in Pyongyang before heading to Beijing, according to Xinhua news agency.

That next stage promises to be contentious even by the bruising standards of the talks that began in 2003.

''We've got to the first mountain in a pretty big mountain range. Yongbyon was the first step in a very tough process,'' said Peter Beck, who analyses North Korea from Seoul for the International Crisis Group, a non-government think tank.

UNFROZEN FUNDS Pyongyang refused to close Yongbyon until Washington cleared away an international snarl-up over some 25 million dollars of its funds unfrozen from a Macau bank as part of the February deal.

North Korea officials had called the bank demand a test of US ''sincerity'' and such testing of wills is likely to shape the forthcoming phase of talks.

Negotiators said Pyongyang must now prepare to permanently ''disable'' the Yongbyon complex and offer a full account of its nuclear activities, which Washington has said included efforts to enrich uranium -- a potential route to nuclear weapons materials that does not need tell-tale reactors.

''While North Korea has started to take the first step, it is important to ensure sure-footed progress towards denuclearisation,'' Japan's Sasae said.

After arriving in Beijing, US envoy Christopher Hill met North Korea's Kim and said he planned to meet his other counterparts before formal talks.

The US State Department said yesterday that International Atomic Energy Agency inspectors had verified the shutdown of Yongbyon and expected to verify the status of four other nuclear facilities, including a spent fuel reprocessing plant that can be used to extract plutonium, by tomorrow.

The impoverished North will get 950,000 more tonnes of oil, security assurances and improved access to international trade if it completely scraps its nuclear arms programmes.

But verifying a full deal would entail sweeping inspections of a regime that has long warded off international intrusion.

After throwing out International Atomic Energy Agency inspectors in late 2002, North Korea quit the nuclear Non-Proliferation Treaty, which the IAEA enforces.

In 2005, Pyongyang declared it had nuclear arms, and last October it alarmed the world with its first test detonation.

''It's still an unanswered question whether North Korea has the will to abandon nuclear weapons,'' said Zhang Liangui, a Chinese expert on the North.

REUTERS SKB KP1523