Envoys Wednesday gave up hope of immediately bringing North Korea back to talks on its nuclear program, going home empty-handed after coming together for a private initiative in Japan.
North Korea, which last year declared it had nuclear weapons, has shunned six-nation disarmament talks since November. It is protesting at US sanctions on a bank accused of money-laundering and counterfeiting on its behalf.
The North sent a negotiator to a closed-door security conference in Tokyo but failed to win a one-on-one meeting with the United States, which insists the communist regime commit to resuming formal negotiations.
"It's really not our job to get them back to the talks. It's their job to get back to the talks," said Christopher Hill, the US chief envoy to the stalled negotiations, who was due later Wednesday in Seoul.
"Once the DPRK comes back to the talks, then we can look back and say we made progress in Tokyo," Hill told reporters, using the North's official name, the Democratic People's Republic of Korea.
Wu Dawei, chief envoy of Pyongyang's main ally China, said six-way talks hosted by Beijing would not resume this month.
"I don't think it will be possible," Wu said, adding however that talks would resume in "due course."
North Korea expert Masao Okonogi, a law professor at Keio University, said the North failed to offer any incentive to persuade other countries that sanctions on the blacklisted Macau-based bank should be weakened.
"I had expected Kim Kye-Gwan to have something in the bag because, if not, it would make the prospects for six-nation talks bleaker. But he didn't," Okonogi said.
South Korean negotiator Chun Young-Woo, who met for two hours overnight with his North Korean counterpart, said the five nations instead showed resolve that Pyongyang should stop linking the resumption of the talks to sanctions.
"We have found here that North Korea has not changed but North Korea has heard a common voice from all other countries participating in the six-party talks," Chun said.
The forum, which has been organised periodically by the University of California at San Diego since 1993, was aimed at reinvigorating the stalled talks through informal dialogue.
Hill and North Korean envoy Kim Kye-Gwan shook hands and spoke briefly during the main session Tuesday, a participant said.
The latest North Korean nuclear crisis erupted in 2002 when the administration of US President George W. Bush, who had labelled Pyongyang part of an "axis of evil" with Iran and Iraq, said the regime was secretly enriching uranium.
The uranium program violated a 1994 accord in which North Korea agreed to give up nuclear development in exchange for US security guarantees and the construction of light-water nuclear reactors.
Charles Kartman, the former chief US negotiator on North Korea who headed the now defunct consortium in charge of the 1994 deal's energy project, said it was difficult by nature to make progress in talks involving six nations.
"I think they will resume. But soon? I don't know," Kartman told AFP on the sidelines of the conference.
In the midst of the rare meeting, host Japan stepped up pressure on North Korea to come clean on its kidnappings of Japanese civilians in the 1970s and early 1980s to train the regime's spies.
China criticized Japan for bringing up the emotionally charged dispute at the sensitive time.
"I think it was a coincidence, but Japan could have delayed the timing," said Wu, China's vice foreign minister.