After a buoyant start that featured contact between the US and North Korean negotiating teams, the parties fell back to more entrenched views on how the denuclearisation of the Korean peninsula should unfold.
With day three of discussions due to start, the two Koreas, the United States, Japan, Russia and host nation China were trying to scrape together a consensus on agreed principles for the first time in three years of inconclusive talks.
North Korea reacted coolly to a US offer dating back to June 2004 to provide security guarantees and South Korean aid in return for the North agreeing to dismantle - not just freeze - its nuclear programmes in a verifiable way.
Pyongyang has insisted on security guarantees and aid pledges before it moves to scrap its weapons programme, and a senior US official told reporters the North Koreans had objected to the proposal that they should move first.
"They were not entirely satisfied by it and had some concerns about the sequencing of obligations, feeling their obligations were frontloaded and the obligations of the other parties were back loaded," the US official told a briefing after the second day of talks.
Flexibility on timing
The US official said the elements laid out in the June 2004 proposal remained the basis of Washington's position but hinted that there might be some flexibility on timing.
"As for timing and sequencing, I think we have to see where we are with the other parties," he said.
"As for timing and sequencing, I think we have to see where we are with the other parties"
Participants were now focusing on agreeing on some form of statement as a framework, "a set of agreed principles on the basis of which we can narrow the scope of issues and lay out an eventual schedule for negotiation of an overall agreement", he added.
A South Korean official said Seoul had proposed that the six adopt a joint document setting out two "pillars", or matching promises, without specifying the sequence of events - which might help bridge the gulf between Washington and Pyongyang.
North Korean demands
North Korea staked out a tough position on Wednesday on the second day of talks, demanding US concessions as the other five outlined proposals for resolving the crisis.
Pyongyang demanded Washington remove nuclear weapons from the Korean peninsula.
The United States, which keeps more than 30,000 troops in South Korea, says it no longer has such weapons in the country.
Hill reassured the North that the
US sees it as a sovereign state
As this long-awaited fourth round of talks began, the two sides seemed to be taking a less confrontational approach than during previous forums spread over almost three years.
"Outpost of tyranny"
At Tuesday's opening plenary session, US Assistant Secretary of State Christopher Hill sought to reassure the North, which months ago Washington had labelled an "outpost of tyranny", that it considered it a sovereign state that need not fear American attack.
The nuclear standoff erupted in October 2002 when US officials accused Pyongyang of pursuing a clandestine weapons programme, prompting it to expel nuclear inspectors.
Early this year North Korea announced that it had nuclear weapons.
It demanded Washington provide aid, security guarantees and diplomatic recognition in return for scrapping them, a sequence that remains at odds with the US position.