"We've come here with three goals in mind," top U.S. negotiator Christopher Hill told reporters Tuesday.
He said the parties wanted to decide on specific standards by which to check if North Korea has told the truth about its past nuclear activities, to set schedules for delivering fuel oil aid to the impoverished country and for disabling its nuclear facilities.
Of the three, setting standards to check North Korea's accounting of its past nuclear activities was likely to dominate discussions, South Korean envoy Kim Sook said Tuesday.
Negotiators will have "intensive consultations on the issue of verification," he said.
Envoys from the six countries - which also include host China, Japan and Russia - have played down expectations and said they expect the process to be difficult.
"I cannot deny that there is a very large gap between the positions of North Korea and the other parties in the six-party talks regarding verification," Japanese nuclear negotiator Akitaka Saiki said.
U.S. officials said in October that North Korea had agreed to allow experts to take samples and conduct forensic tests at all of its declared nuclear facilities and undeclared sites.
But Pyongyang said last month it agreed only to letting nuclear inspectors visit its main atomic complex, view related documents and interview scientists, but would not allow outside inspectors to take samples from the complex.
China, which met separately with each of the other five delegations Monday, was expected to circulate a draft agreement on the process on Tuesday, envoys said.
"I asked China to play an active role to produce (the verification) protocol at a difficult time," Kim said. Chinese envoy Wu Dawei said his country "will do what it should do."
A consensus was reached among the six parties to ship all the promised economic aid to North Korea - 1 million tons of heavy fuel oil or equivalent aid - by the end of March, Kim said, without elaborating.
The economic aid has been a sticking point in the negotiations.
Japan has refused to send any aid, saying Pyongyang must first address the kidnappings of more than a dozen Japanese citizens in the 1970s and '80s.
North Korea responded by vowing to ignore Japan at the latest talks. Its envoy, Kim Kye Gwan, said Monday that the parties should debate whether Japan was qualified to take part in the disarmament talks, the Kyodo news agency reported, citing an unnamed Japanese official.
North Korea has issued similar warnings in the past, but Tokyo has continued to attend the negotiations that began in 2003.
In bilateral talks with South Korea, Pyongyang agreed to export its unused fuel rods to other countries. Asked whether South Korea will buy the fuel rods, Kim said no decision had been made yet.
Seoul has said in the past it would consider buying the North's fuel rods if they can be adapted to work in South Korea's power-generating nuclear reactors.
