The United States and North Korea held key talks in Singapore on Tuesday over the communist state's nuclear disarmament but the US warned efforts to resolve an impasse were running out of time.
US envoy Christopher Hill and North Korea's Kim Kye-Gwan began their talks at about 11:00 am (0300 GMT) at the United States embassy, a US official said.
"I will be discussing the fact that we are kind of running out of time," Hill told reporters at his hotel before heading to the meeting.
"We're not looking for an agreement. I think we're looking to have a consultation on some of the issues that have kept us apart for several months and certainly I will be discussing them."
Hill's comments added further weight to statements he made after arriving in Singapore on Monday night from Indonesia.
"We can't afford any further delays here," he said then. "We do need to make some progress very soon."
Washington has been pushing North Korea to come clean on its entire nuclear programme as a key step in a 2007 six-nation denuclearisation deal that also involves China, Japan, Russia and South Korea.
Asked Tuesday morning what he expected from the Singapore meeting, Hill said: "We've got a pretty open agenda... We will see how it goes."
He hinted it could be a long session, saying: "We have a lot of hours today."
South Korean media reports have suggested Kim could be prepared to hand over a document that addresses concerns about its alleged secret uranium enrichment programme and cooperation with Syria.
Hill and Kim last met in Geneva in mid-March.
The 2007 six-party deal grants North Korea -- which tested an atomic weapon in 2006 -- energy aid and major diplomatic and security benefits in return for full denuclearisation.
The current phase of the deal required the North to disable its main plutonium-producing plants and declare all nuclear activities by the end of last year.
The North says it submitted the declaration in November. But the United States says it has not accounted for an alleged secret uranium enrichment programme or for alleged proliferation to Syria.
"What we need to do is to try to resolve the issue of the DPRK's responsibility to provide a complete and correct declaration... 'complete and correct' means just that," Hill said on Monday.
He said the aim was to hold another six-party meeting "very soon".
Asked on Tuesday about a Japanese media report that said North Korea did not understand the US position, Hill responded: "No, it is not possible. They know precisely why, what the issues are and they understand that we didn't want to meet unless we could achieve something."
South Korea's Hankyoreh daily, which reported that a breakthrough could be in the offing, said the US had vowed not to make public the so-called "confidential minute" and not to exploit it for political purposes.
The talks coincide with increasing tensions between Seoul and Pyongyang. Conservative Lee Myung-Bak, who took office as South Korea's new president in February, has angered the North by adopting a tougher line on ties.
North Korea kept up the rhetoric on Monday, accusing Lee of pushing the peninsula closer to nuclear war and telling Seoul it should order the United States to withdraw its "nuclear weapons massively stockpiled in South Korea."
The US, Seoul's long-time military ally, says it withdrew the last of its atomic weapons from the peninsula in 1991.
On Thursday, North Korea announced it was suspending all dialogue with the South and closing the border to Seoul officials. Hill said the talks were held in Singapore because of "logistics, and it's worked very well for us."
From Singapore, Hill was to travel on Wednesday to Beijing, where he said he would meet South Korean, Japanese, and probably Russian officials as well as the Chinese.