A Chinese diplomat said Monday that North Korean negotiators were warming toward a resumption of talks on ending the North's nuclear weapons program, but the top U.S. envoy said he has no plans to meet directly with his counterpart from Pyongyang.

North Korea has shown "some" signs of positive commitment, said Wu Dawei, China's top nuclear envoy, after meeting twice with the North Korean delegation on the sidelines of a two-day security forum in Tokyo.

"We can expect some progress," he told reporters Sunday, without giving details. "We discussed what should be done to achieve a breakthrough."

Wu's were some of the first positive comments in a flurry of diplomatic meetings that has otherwise produced little progress in resuming the stalled nuclear talks.

North Korea has boycotted the dialogue since November, citing what it calls a hostile U.S. attitude illustrated by financial sanctions Washington imposed on North Korean companies for alleged financial crimes.

U.S. Assistant Secretary of State Christopher Hill has urged North Korea to return to the talks, but said he has no plans to meet one-on-one with the North Korean side while in Tokyo.

"The North Koreans have not yet decided to return to the talks," Hill said after arriving at Tokyo's Narita airport, adding that both countries held unproductive meetings on the matter in January and March.

"I'm not sure there's much more I can talk to them about," he said. "Everybody else is in, so we're waiting for them."

The North agreed in the six-nation talks last year to abandon its nuclear program in exchange for aid and security guarantees, but the talks foundered and there has been little progress on implementing the accord.

North Korea has refused to restart talks unless the financial restrictions _ imposed on a Macau bank and North Korean companies _ are lifted, but Washington maintains the sanctions are unrelated to the nuclear talks and will stay in place.

The presence of delegates from all six nations involved in the talks _ the U.S., the two Koreas, China, Japan and Russia _ at the private conference in Tokyo has raised hopes they could find a way through the impasse.

Speaking at Monday's opening ceremony, Susan Shirk, co-organizer of the talks, said the conference "might be helpful" for officials involved, but cautioned, "This forum is not a substitute for the official six-party talks."

The forum's agenda will focus on energy, verification processes regarding the North's nuclear program and ways to ease tensions on the Korean Peninsula, according to the sponsors, University of California, San Diego.

For several days, delegates from Japan and South Korea have held separate meetings with their North Korean counterparts, and each other, but have made little progress.

North Korea's chief delegate, Kim Kye Gwan, said Monday he is prepared to meet bilaterally with the U.S., but has not backed away from his insistence that Pyongyang will only return to the six-way talks if the U.S. lifts the financial sanctions.

Chun Young-woo, South Korea's top negotiator, said a trilateral meeting with Hill and Japanese counterpart Kenichiro Sasae late Monday had yielded "several ideas" on how to hammer out a compromise.

"It's still too early to say that we are optimistic or pessimistic. Let's wait and see," Chun said.

Sasae said the trio agreed to persuade Pyongyang it was in its interest to return to the talks. He met with Kim earlier on Monday afternoon, their second meeting since Kim's arrival in Tokyo, with no breakthrough.

China's Wu also met with the Japanese and Russian delegates, said Li Wen Ling, a Chinese Embassy spokesman. Wu and Chun were slated to hold separate meetings with Hill Tuesday.