On Friday, conflicting signs emerged after Washington said results were positive but the North accused its old foe of blocking progress with "a hostile policy".
The United States refused to back down from its hard-line stance on North Korea's nuclear weapons. Washington apparently refused to give any ground despite a North Korean offer to disarm if the US took a "corresponding" measure.
Yet US Secretary of State Colin Powell gave an upbeat assessment of talks that also involve South Korea, China, Japan and Russia.
"The results of the first two days of meetings are positive," Powell told the Senate Budget Committee in Washington. "There's a promising attitude that is emerging from those meetings and hopefully we can move in the right direction there."
"The United States is saying that it can only discuss our demands after we give up all nuclear programmes, including for peaceful purposes, as it continues with its stale demand that we give up nuclear programmes first despite our flexible position," the North Korean embassy said in Beijing.
"This is a 'salami tactic' of slicing the sausage very thinly to maximise compensation"
Yonhap news agency,
"It is because of this that there has not been a breakthrough in the solution of the problems," it said.
North Korea's Yonhap news agency said the move was designed to be able to extract compensation for both programmes during drawn-out negotiations.
"This is a 'salami tactic' of slicing the sausage very thinly to maximise compensation," it said.
A third full session of talks lasted little more than an hour and a half on Friday morning, with North Korea's proposal to freeze its nuclear weapons programme on the table and a South Korean, Chinese and Russian-backed plan to offer energy
aid in exchange.
In the quest to find a compromise, the talks were extended by a day. "The talks have been extended by one day. The talks will continue on Saturday 28 February," South Korean delegation spokesman Shin Bong-Kil said.
At the very least, China wants all sides to issue a joint document at the conclusion of the talks setting out what has been achieved so far and for working groups to be established to carry the process forward.
The first round of talks last August ended in an impasse.
The nuclear crisis erupted in October 2002 when US officials said North Korea had admitted to a covert programme to enrich uranium for nuclear weapons. Pyongyang has since denied saying any such thing.