"I'm not here telling you the negotiations have failed. We have another day," [Christopher Hill] said after a fourth and long day of meetings in Beijing.

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

"Because this round could be the crossroads, today's talks took place in an atmosphere of heightened tension," Japan's negotiator Kenichiro Sasae said.