North Korea must halt its nuclear weapons programme now to show it is taking negotiations on disarmament seriously, the chief US negotiator said on Thursday on the second day of six-party talks in Beijing.
But North Korean delegates were quoted by a source close to the talks as saying they had no "will" to negotiate with the United States, Japan's Kyodo news agency said.
Negotiators said the three-day talks due to end on Friday would focus on the logistics of further bargaining after a framework for disarmament was agreed in September.
But the perennial issue remains trust between the two main protagonists, Washington and Pyongyang.
"The time for them to stop producing nuclear material is now," chief US negotiator Christopher Hill told reporters.
"The faster they move, the faster we move, the faster everybody moves, and I think the faster the DPRK can be reintegrated into the world," Hill said, referring to Pyongyang by its official name, the Democratic People's Republic of Korea.
Hill said he would contemplate travelling to North Korea if it would help the talks. Earlier in the day, Hill said: "You know how you build up trust? You live up to the agreement ... You can build up trust through actions."