Six-nation talks on North Korea's nuclear programme have ended in Beijing without a major breakthrough.
Talks are focused on programmes at the Yongbyon nuclear site
The United States hailed the meeting as "very successful", but North Korea said there had been "no substantive and positive result".
China cited a "complete lack of trust" between the US and North Korea, and said serious differences remained.
The parties agreed to hold more talks before the middle of the year and set up working parties to examine issues.
An unnamed US official told reporters the talks had placed America's demand for the complete dismantling of North Korea's nuclear programme "more on the table than ever".
"The event has exceeded my expectations in a very important
respect," the official was quoted by Reuters as saying.
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"It's been very successful in moving the agenda towards our goal of complete, verifiable and irreversible dismantling [CVID] of DPRK [North Korea] nuclear programmes."
North Korea has traditionally offered only to freeze its nuclear programme in return for economic and energy aid and security guarantees from Washington.
The BBC's Charles Scanlon in Beijing says analysts noted signs of flexibility in the American position - it acquiesced in a regional offer to provide energy aid to the North in return for a nuclear freeze and made it clear that security guarantees and diplomatic relations were on the table if an agreement could be reached.
North Korea was far more negative, blaming the US for a lack of significant progress.
"We were denied the joy of a corresponding attitude by the US side," North Korea's chief delegate Kim Kye Gwan said after the talks.
"The United States is not willing to resolve this issue fundamentally."
Chinese Foreign Minister Li Zhaoxing said some progress had been made but urged caution.
"Differences, even serious differences, still exist," he said.
China's chief delegate, Vice Foreign Minister Wang Yi, said more discussion was needed on the scope of North Korea's offer to freeze its nuclear activities and America's demand for an complete end to Pyongyang's nuclear programmes.
Russia's Interfax news agency quoted Russian Deputy Foreign Minister Alexander Lossyukov as saying "progress, modest but a step forward" had been achieved at the talks.
The talks, involving the US, Russia, China, Japan and North and South Korea, were the first since a round last August ended without substantial progress.
One of the main stumbling blocks has been America's insistence that North Korea scrap an alleged uranium-enrichment programme to build nuclear weapons.
The current crisis erupted in October, 2002, after a senior US envoy said North Korean officials admitted to having such a programme, but North Korea has denied the assertion.
"The DPRK denials are there, but seem only to result in a
self-isolation," Reuters quoted the US official as saying.
North Korea says, however, it has reprocessed thousands of spent nuclear fuel rods at the Yongbyon nuclear facility, from which extracted plutonium can be used to manufacture nuclear bombs.
The reclusive Stalinist state claims to have nuclear weapons, which the US believes might number "one or two".