The US negotiator at discussions on North Korean nuclear status says little progress has been made during the first day of the latest round of talks.
The US envoy described the meeting as 'businesslike'
Christopher Hill said North Korea is now asking for a light-water nuclear reactor - a new demand which was not part of the draft agreement.
The six-party negotiations also involve South Korea, China, Russia and Japan.
They were suspended in August over US demands for North Korea to dismantle all of its nuclear facilities.
"It was a rather lengthy meeting but I must say it was a meeting in which we did not make a lot of progress," Mr Hill told reporters in Beijing.
"There are not too many other ways I know how to say 'no'."
He added the latest demand would be a "major problem" for the talks, for which no end date has been set.
He explained the such a reactor would cost $2-3bn (£1.1-1.6bn) and would take about 10 years to build, and insisted the North accept a South Korean offer to use its electricity through power cables across the border.
The assistant secretary of state for East Asian and Pacific affairs underscored that agreement needed to be reached on the removal of North Korea's "terrible weapons" before other demands could be looked into.
Pyongyang on its part wants aid and diplomatic incentives and be granted the right to keep civilian programmes first.
South Korea has offered to supply the North with 2,000 megawatts of electricity - roughly the North's current total power output.
But the South Korean chief envoy, Song Min-soon, said on Wednesday that once the dismantlement of nuclear weapons and programmes was completed, Pyongyang should be granted "the right to peaceful use of nuclear energy".