The six-nation talks with China, South Korea, Japan and Russia went into the recess still deadlocked over the Stalinist north's nuclear ambitions, despite a fortnight of intense and wearying negotiation in the Chinese capital.

Talks were to resume the week of August 29 but with the US and North Korea again trading barbs, it was unclear how to move forward in the three-year standoff with North Korea, which again said it was making nuclear weapons.

"We decided to have a brief recess so delegations can go back to report to their respective governments, further study each other's positions and resolve differences which still exist," China's chief envoy, Wu Dawei, told reporters.

This was the crux of a statement winding up 13 days of talks, and fell short of the original plan for some kind of joint agreement setting out how North Korea would abandon nuclear weapons and what it would get in return.

After nearly two weeks of sometimes heated and late-night negotiations, the key sticking point boiled down to whether the North should be allowed to run nuclear programs for peaceful, energy use.

"They not only want the right to use nuclear energy, but the right to use light-water reactors. That is simply not on our table," the US envoy to the talks, Christopher Hill, told reporters.

"Frankly, the DPRK (North Korea) would like to put in the light-water reactors (to a proposed joint document) but no one else wants to do that.

"It is quite appropriate for them to go back to their capital to tell them that the light-water reactor is simply not on the table," he said.

A Japanese government official said all five other nations agreed that now was not the time for Pyongyang to insist on the peaceful use of nuclear energy.

"There is no major discrepancy among the five," the official said.

The construction of two light-water nuclear reactors for the power-starved North is part of a 1994 agreement between the reclusive state and the United States.

That deal committed Pyongyang to freezing and eventually dismantling its graphite-moderated nuclear reactors, which can produce weapons-grade nuclear material more easily.

But the project was suspended in October 2003 following the eruption of the current crisis one year before, when the United States said North Korea admitted to having a secret uranium enrichment program.

It prompted North Korea to withdrew from the nuclear non-proliferation treaty (NPT). It has since claimed to have nuclear bombs.

North Korea's chief delegate Kim Kye-gwan said it was the right of every country to use nuclear power for peaceful purposes and put the onus on the United States to back down if it wanted to see progress.

"During this round of talks I had expected the United States to accept our demand (for peaceful nuclear activities) but the United States did not make such a decision," he told reporters.

"During the recess I hope the United States will change its policy," he said.

Kim added that the United States must also commit not to attack and remove the so-called nuclear umbrella for South Korea, repeating that his country was building nuclear bombs as a deterrent.

Japanese envoy Kenichiro Sasae said North Korea must build trust by rejoining the NPT before expecting any agreement on nuclear programs for civilian use.

"North Korea should first regain trust of the international community by such measures as its return to the NPT," he said.

Pyongyang has offered to do this but only "if the nuclear issue finds a satisfactory solution."

The talks are also struggling to overcome another hurdle -- in exchange for dismantlement, the North has also demanded normalization of ties with the United States as well as economic assistance and security guarantees.

The United States has repeatedly said that the North needs to give up its weapons programs before it gets aid and energy.

A collapse of the negotiations could tempt Washington to take the issue to the UN Security Council for possible sanctions. Pyongyang has warned that sanctions would be viewed as a declaration of war.