SEOUL: The door has creaked open in talks on ending North Korea's nuclear ambitions but analysts agreed on Monday there was a long way to go because Pyongyang still sees atomic weapons as a crucial part of its survival strategy.

Host China, the two Koreas, Japan, Russia and the United States ended a third round of talks in Beijing inconclusively on Saturday. Yet analysts - and in particular South Korean officials, including President Roh Moo-hyun - said this was the most productive session so far.

"Doors have opened," said Masao Okonogi, a Korea expert at Tokyo's Keio University. "Until now, both the United States and North Korea stuck to their basic principles. But this time, I think they took it a step further."

US officials put forward Washington's first detailed proposal, offering security guarantees and South Korean aid in return for North Korea agreeing to dismantle its nuclear programmes.

North Korea said it was ready to freeze its plutonium-based nuclear activities. "We finally have 'negotiations' worthy of the name," said the Hankyoreh newspaper, a left-wing South Korean daily.

But central to the undiminished differences between the United States and North Korea was Washington's demand Pyongyang disclose its uranium enrichment programme, which can be used for making bombs. The North continued to deny it had such a scheme.

"I still think North Korea is very determined to develop a nuclear programme and it is much easier to hide a highly enriched uranium programme than a plutonium programme," said Choi Jin-wook of Seoul's Korea Institute for National Unification think-tank.

"They still want to keep it secret and if possible they want to develop it," he said. "Or they want to use it as a bargaining chip later." Wang Yizhou, deputy director of the Institute of World Economics and Politics at the Chinese Academy of Social Sciences, said uncertainties lay ahead, but he was cautiously optimistic.

"I am convinced the future process will not be very simple or smooth sailing. It could be a zigzag for multiple reasons and blame cannot be completely put on the DPRK," said Wang, whose institute is a government thinktank.

DPRK is short for the North's official name, the Democratic People's Republic of Korea, a military-minded country ruled by the world's first communist dynastic successor, Kim Jong-il.

Choi said North Korea's determination to have a nuclear arsenal went far beyond its deterrent value. "It is very closely related to North Korea's intentions of how to run their system, the country, it's long-term programme of reform.

This is not only the problem of the nuclear issue like in Ukraine or like in South Africa," he said. "It's a very, very essential part of North Korea's survival strategy."

Choi and other analysts said even if the broad principles of a first-stage freeze could be agreed, the tight timetable for working-level talks before the fourth round of negotiations in September meant negotiating details on verification, inspections, aid and dismantlement would be complex and controversial.

"There is still a long way to go," said the English-language edition of Japan's Asahi Shimbun. "Sharp confrontation may erupt when officials of the participating nations start mapping out details of the freeze."

Conservative South Korean newspapers and President Roh, whose administration is liberal and left-leaning, were unusually united in giving upbeat assessments of the latest talks, describing progress as significant and substantial, although the dailies did not disguise the task ahead.

Hankyoreh, the left-wing daily, said a major factor would be whether the United States administration's hardliners would try to prevent progress ahead of the November presidential election.

Tokyo's Okonogi made a similar point, noting further progress could be made, depending on North Korea's response. The North Korean foreign ministry said the talks had been positive but close examination of the American proposal showed little new. -Reuters