North Korea's envoy promised to make "sincere efforts" as diplomats prepared to resume six-nation talks Wednesday aimed at stripping Pyongyang of its nuclear weapons program, although analysts warned against expecting a breakthrough.

China says the talks in Beijing — the fifth since 2003 — will last three days before a recess to let the diplomats attend an Asia-Pacific economic forum in South Korea. Participants in the nuclear talks are the two Koreas, China, the United States, Japan and Russia.

The last round of talks ended in September with North Korea promising to disarm in exchange for aid and a security guarantee. But negotiators haven't taken up the most difficult issues: how the North will disarm, and how to verify it.

North Korea has raised doubts about its intentions by demanding it be given a civilian nuclear reactor before it disarms — a demand the United States has rejected.

Pyongyang appears to be dragging its feet, said Peter Beck, the Seoul-based director of the North East Asia Project for the International Crisis Group, an independent think tank.

"I don't think they're serious about progress yet," he said. In the meantime, he said, "Washington has no choice but to go along with this charade."

Even host China tried to moderate expectations, saying this week's meeting could be considered a success even if it produces no written agreement.

"I do not think that progress of the talks needs to be measured by the signing of a document," Foreign Ministry spokesman Liu Jianchao said Tuesday.

A joint statement at the end of September's talks sidestepped the North's demand for a nuclear reactor, saying it would be discussed "at an appropriate time."

"We are willing to make sincere efforts at this round of the talks to fulfill the spirit of the joint statement," North Korea's envoy, Kim Gye Gwan, was quoted as saying by China's official Xinhua News Agency.

The North's leader, Kim Jong Il, promised a visiting Chinese President Hu Jintao last month to press ahead with the talks. Kim said the North was committed to a nuclear-free Korean Peninsula.

Yet Hu's promise of economic help might have taken the pressure off Pyongyang to make a deal, Beck said.

Beck said Hu's pledge suggested that the governments that are trying to get North Korea to give up nuclear development were failing to coordinate the timing of their "carrots and sticks" — the timeline for the North to meet conditions in exchange for aid.

Further, the issues to be resolved are too vast, said Liu Jiangyong, a specialist in international relations at Tsinghua University in Beijing.

"We do not expect breakthroughs to be achieved in the next three days in all issues mentioned in the joint statement," Liu said.

In Seoul, South Korean President Roh Moo-hyun said the talks are the only way to resolve the dispute, which erupted in 2002.

"Although it may take some time, failure is inconceivable," Roh said at a luncheon with foreign journalists.

South Korea's Deputy Foreign Minister Song Min-soon said it was premature to discuss setting up groups of experts to examine the details of the disarmament process, the South's Yonhap news agency said.

Song said he expected the participants to use this three-day session to examine one another's positions.

"We can advance the talks when similarities and differences come out," he told reporters in Beijing, according to Yonhap.