Representatives from the six nations - the US, China, Russia, Japan and the two Koreas - held a series of meetings on the sidelines of an academic conference in Tokyo hoping to revive negotiations.
But as delegates prepared to leave Tokyo on Wednesday, officials said the North Koreans were sticking to their refusal to rejoin the talks in protest against US sanctions imposed on North Korean companies for alleged financial crimes.
Wu Dawei, the Chinese chief negotiator, said before returning to Beijing that there was no possibility of a resumption of the talks by the end of April, saying the sanction issue was the primary stumbling block.
"We'll continue to make efforts," Wu said. "At the moment, our prospects are still unclear."
Christopher Hill, the US assistant secretary of state, met counterparts from Japan and South Korea on Wednesday morning, and said the five nations urging North Korea back to the talks were forming a common strategy.
"North Korea's position has not changed"
US assistant secretary of state
Hill, who was expected to go to Seoul later in the day, said the decision was now up to North Korea.
"I don't think it's up to us to get the DPRK back to the talks," he said, using the country's official name, the Democratic People's Republic of Korea.
Chun Young-woo, the South Korean chief negotiator, also leaving on Wednesday, said the North Korea's linkage of the US financial sanctions to the nuclear talks was not in Pyongyang's best interest.
"North Korea's position has not changed," Chun said.
Speculation had been high that Hill would meet the North Korean delegate, Kim Kye Gwan, but such an official meeting never materialised. The two had a brief encounter on Tuesday, said Chun, but it was not a full meeting.
Hill reiterated on Wednesday that he was not in Tokyo to meet the North Koreans, and Chun also said that such a meeting later in the day was unlikely.
North Korea has refused to restart the talks unless the financial restrictions - imposed on a Macau bank and North Korean companies - are lifted.
Washington maintains that the sanctions are unrelated to the nuclear talks and will stay in place.
Hill on Tuesday said the US had frozen $24 million of the impoverished communist nation's holdings. The sanctions were imposed to counter alleged counterfeiting and other wrongdoing.
The Tokyo gathering had raised hopes of restarting talks that have been stalled since last year on ending North Korea's nuclear programme in exchange for aid. Pyongyang has boycotted the six-party nuclear talks since November.
Meanwhile, Hill described his Tuesday morning meeting with China's Wu Dawei as "very excellent" and said Beijing was committed to resolving the stand-off through dialogue.
Chun told reporters after meeting Hill on Tuesday that North Korea seemed to be considering talks, but that "it is difficult to say at this point whether it will lead to a resumption."
North Korea's Kim later held a meeting with the Japanese and said the two sides discussed "how to break the nuclear deadlock," but declined to give any details.