When negotiations resume on Tuesday, the six nations involved are expected to work for agreement on a statement of principles as a framework for continuing the dialogue, rather than significant breakthroughs.

"Basically we are looking at several possibilities in Beijing and it is hard to know which way the talks will go," said Kim Taewoo, a nuclear policy expert at the Korea Institute for Defense Analyses in Seoul.

"First, they could be successful and we could be looking at an agreement. Second, we could see improvement. Third, the talks could result in further aggravation and ill-feeling. Fourthly, they could simply collapse.

"I would say the possibility for one and four is very slim so it has to be two or three, but it is very hard to say which."

After a fortnight of tough negotiation in Beijing failed to find common ground, the fourth round of talks broke up for three weeks on August 7 -- but North Korea refused to return as scheduled, citing US-South Korean war games.

In addition to the military exercises, Pyongyang was irked by Washington's appointment of a US presidential envoy on human rights in North Korea.

But they set a date for this week and the other parties involved -- Japan, South Korea, China, Russia and the United States -- agreed.

The key sticking point remains North Korea's demand to retain the use of nuclear facilities for peaceful purposes, which the United States has rejected.

Joseph Cheng, an expert on North Asia based at City University of Hong Kong, said there was reason to be upbeat despite the apparent deadlock.

"I believe there are some hopeful signs. China has been exerting a lot of pressure and the US has shown much more pragmatism. This has left more room for agreement. In other words, there is a considerably better foundation," he said.

Cheng said it was possible that Washington will agree to recognize in principle that North Korea has the right as a sovereign nation to the peaceful use of nuclear energy, in return for some sort of verification mechanism.

But it will not likely happen at this round of talks.

"It will take time and there will be no immediate breakthroughs," Chen said. "But someone has to take the first step."

Tom Lantos, a US Congressman who travelled to North Korea this month for meetings with senior officials, said Pyongyang appeared to have "taken on board" that something concrete must be achieved.

"The fact remains that unless a set of principles can be agreed upon as a framework for continuing the dialogue, there is nothing else to talk about," he said.

Like Iran, the North argues that it has a sovereign right to have light water reactors (LWT) for civilian use. The United States fears it could use them to clandestinely develop weapons-grade material.

The LWTs were to have been built by a US-led consortium before 2003 to replace North Korea's existing graphite-moderated reactors, which can produce weapons-grade plutonium, under a defunct 1994 nuclear agreement.

But their construction was suspended amid the nuclear standoff, which prompted North Korea to withdraw from the nuclear non-proliferation treaty.

"For the Bush administration, it does not want to strike a deal that looks like the 1994 deal," said Masao Okonogi, an expert on North Korea and professor of international relations at Keio University in Japan.

The United States argues that a package being put together at the talks includes conventional energy supplies that would replace the energy capacity of the LWTs.

The current showdown began in October 2002 when the United States accused North Korea of having a secret uranium-enrichment program in violation of the 1994 pact.

Pyongyang has denied the charges but declared in February this year that it had already built nuclear bombs.

Since 2003, the talks have aimed to persuade North Korea to abandon its nuclear weapons in exchange for diplomatic and economic benefits as well as security guarantees.

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