Beijing ? Talks on dismantling North Korea’s nuclear programs were on the verge of foundering Sunday as negotiators failed to overcome differences on the North’s demands for energy aid but scheduled a final day of meetings.

U.S. Assistant Secretary of State Christopher Hill said the talks had snagged on the amount of energy assistance Pyongyang would receive as an inducement for disarming. But he said that a deal could still be reached today, the last scheduled day for the negotiations.

“I’m not here telling you the negotiations have failed. We have another day,” Hill said after a fourth day of meetings in Beijing.

The current round of six-nation talks began on a promising note, after the United States and North Korea signaled a willingness to compromise. But since the talks entered the second day, envoys have said negotiations were becoming stuck on a single issue: energy assistance.

“We’re not interested in an energy deal. We’re interested in a de-nuclearization deal,” Hill said, adding that he had a “lengthy and very frank” discussion with the North Koreans on the issue.

Envoys questioned whether the six-nation talks that have plodded on in fits and starts since 2003 would be worth pursuing if the current session ends without resolution.

“I think we have a real problem if we can’t reach an agreement on this,” Hill said.

“Because this round could be the crossroads, today’s talks took place in an atmosphere of heightened tension,” Japan’s negotiator Kenichiro Sasae said. “The situation remains severe.”

South Korean envoy Chun Yung-woo said the sticking points touch on vital interests of many of the parties.

“It’s not a situation where a breakthrough is in sight,” he said.

Negotiators had hoped the talks would result in North Korea’s first concrete steps to dismantling its nuclear programs – especially critical since Pyongyang’s successful nuclear test in October.

Envoys have shown rising frustration at North Korea’s intransigence, with the Japanese envoy earlier Sunday calling North Korean demands “excessive.”

“This is the problem, and unless they change their thinking, an agreement will be difficult,” Sasae said.

Russian Deputy Foreign Minister Alexander Losyukov expressed skepticism that the negotiators could reach agreement on how much assistance North Korea should receive.

South Korean and Japanese media reports gave varying accounts of how much energy the North was demanding, from 2 million kilowatts of electricity – an amount equal to all of North Korea’s current generating capacity – to 2 million tons of heavy fuel oil.