The six-party talks have been marked by unusually frequent contact between Washington and Pyongyang, the main protagonists in a crisis now nearly three years old, creating a more positive atmosphere than at three previous inconclusive rounds.
But as the open-ended talks stretched into a seventh day, envoys from the two Koreas, the United States, Japan, Russia and China were still struggling to hammer out a statement of basic principles.
The statement was not expected to address the crucial issue of whether North Korea should dismantle its nuclear facilities as a precondition to aid and security guarantees, as the United States wants, or whether the assurances should come first - the heart of the disagreement between Washington and Pyongyang.
"Overnight, there has been a second draft produced ... The drafting committee will again look at this draft," US chief negotiator Christopher Hill told reporters.
"There is still a lot of language in the draft in which the various delegations have some differences," he said, adding it was a "tough process" that would likely go beyond Monday.
Hill said the new draft included mention of South Korea's offer to supply the North with 2000 megawatts of electricity if it dismantled its weapons programmes. That is roughly equivalent to the power-strapped state's total output.
But Pyongyang voiced concern over the proposal.
S Korea's Song Min-soon (R): Frame-
work for denuclearisation is set up
"North Korea is worried that the deal could pose a security threat to the North," a diplomatic source close to the talks told Reuters.
"North Korea's worries are centred on what if South Korea cut off supplies for any reasons," he said.
South Korean envoy Song Min-soon said the six parties had agreed only to set up a framework for eventual de-nuclearisation of the Korean Peninsula after weekend talks that a Japanese delegate said were marked by "fierce exchanges".
Any joint statement would mark a breakthrough at talks where past progress was measured by whether delegates could even agree to reconvene.
Deputies were consigned on Monday to another day of poring over the revised text presented by the talks' Chinese hosts.
China's initial draft called on Pyongyang to abandon its "nuclear weapons programmes and related programmes" in return for the other five providing security, economic aid and improved ties, a diplomatic source told Reuters.
"It is very important to secure commitments or a strategic decision from North Korea to abandon all its nuclear programmes"
It did not address who should move first or if the parties should move simultaneously, avoiding the crucial issue of timing.
"It is very important to secure commitments or a strategic decision from North Korea to abandon all its nuclear programmes," a Japanese delegate said.
The United States also demands verifiable destruction of North Korea's weapons programmes before it will provide security guarantees and aid for the poor, diplomatically isolated country.
The crisis erupted in 2002, when Washington accused Pyongyang of pursuing a covert uranium-based weapons programme in addition to its mothballed plutonium-based activities at Yongbyon.
The North responded by expelling UN nuclear inspectors, withdrawing from the nuclear Non-Proliferation Treaty and breaking the seals at the Yongbyon complex.
The stakes rose in February, when Pyongyang announced it had nuclear weapons and demanded aid, assurances and diplomatic recognition from Washington in return for scrapping them.
Despite the lack of progress at the talks, the frequent one-on-one meetings on the sidelines between North Korean and American negotiators were seen as a positive step, and marked a change from previous rounds that featured only brief exchanges.
At past rounds of talks North Korea's delegation called news conferences to denounce the United States. This time its foreign minister announced that Pyongyang would be willing to rejoin the nuclear Non-Proliferation Treaty if the standoff were resolved.
But he listed several conditions for the resolution, including removing US nuclear weapons from South Korea - weapons Washington says it no longer keeps there.