North Korea's nuclear envoy sat down with top negotiators for the United States and China on Tuesday, an unannounced meeting aimed at reactivating stalled six-nation talks on persuading North Korea to abandon nuclear weapons.

North Korean Vice Foreign Minister Kim Kye Gwan said before the talks with Assistant Secretary of State Christopher Hill and Chinese Vice Foreign Minister Wu Dawai got started that the timing of the next round of six-party talks "depends on the United States."

"There are too many outstanding issues" and both parties should narrow their differences, Kim told reporters on arrival at the airport.

"I said on Oct. 31 that we can enter the talks at any time," he said. "I said that because we can do that from a dignified position as we have taken defensive measures through our nuclear test to counter sanctions and pressure against us."

Chinese Foreign Ministry spokeswoman Jiang Yu said the discussions, which included bilateral and trilateral meetings between the three delegates, were ongoing, and did not give any details.

"We hope all sides can grasp this opportunity and take a flexible, pragmatic, and constructive approach in order to realize the early resumption of six-party talks," Jiang said at a regular briefing.

Kim's trip to Beijing — a rare foreign visit for him — and the presence of other negotiators improved the prospects of compromises to give new life to the disarmament talks, which have been at an impasse for more than a year.

Officials have yet to determine an exact date for the next round of negotiations, which also involve Russia, Japan and South Korea.

Late Tuesday evening, Hill and Kim separately left the Diaoyutai State Guesthouse, where the meetings were held. Neither spoke to the media.

An unannounced meeting between Hill and Kim last month in Beijing led to Pyongyang agreeing to return to the arms negotiations amid heightened tensions after its first nuclear test on Oct. 9.

"The issue for us is to make sure we are extremely well-planned and ready for the six-party talks, which we do anticipate will get going at some point very soon," Hill said when he arrived on Monday.

Hill met separately with South Korea's nuclear envoy, Chun Yung-woo, and Wu on Tuesday morning, said U.S. Embassy spokeswoman Susan Stevenson. She did not have any details on the talks.

Japan's representative Kenichiro Sasae told Japanese reporters that he had also held bilateral talks with Wu and Hill.

North Korea agreed in September 2005 to abandon its nuclear program in exchange for security guarantees and aid. But Washington imposed financial sanctions against a Macau-based bank on suspicions it was laundering counterfeit money for the North Koreans. Angered by the move, Pyongyang withdrew from the talks two months later.