Christopher Hill, the top US envoy to the talks, said, "We're not looking to provide energy assistance so that they could avoid taking the further steps on denuclearisation."
"I think we have a real problem if we can't reach an agreement on this."
"North Korea is making a fool out of Bush and the Neocons. It is amazing that the more stubborn the North Koreans the more, they are rewarded by so many goodies"
B Humble, UK
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Negotiators will now have one more day to seek a deal and none sounded hopeful.
Chun Yung-woo, the South Korean envoy, said: "A breakthrough is not in sight."
He said the disputes were about the scope of energy aid "and the scope, pace and range of the North's actions to denuclearise".
"The core contentious points have boiled down to a narrow range, but we are continuing to make efforts to bridge the gap."
A Pyongyang newspaper blamed the logjam on US "betrayal", saying Washington was not honouring pledges.
Behind the energy demands, the impasse at the six-party talks appeared to reflect abiding distrust between North Korea and the other countries, especially the United States.
The six-party talks have failed to reach agreement on specific disarmament steps despite over three years of the stop-start negotiations.