U.S. chief negotiator Christopher Hill told reporters before leaving Beijing: "I would say that there was a lot of agreement among a majority of the delegations there, but ultimately the DPRK (North Korea) was not ready to reach a verification protocol with all the standards that are required."
The six countries - the two Koreas, the U.S., China, Russia and Japan - discussed a Chinese-drafted verification protocol on means of probing North Korea's past nuclear activities.
China, as host nation, released a statement saying: "the sides highly value the progress reached toward signing an agreement on verification."
However, Chinese Foreign Ministry spokesman Qin Gang told journalists that differences remained between the negotiators.
Hill said no date had been agreed for the next round of six-nation talks.
Currently, the main stumbling block in the negotiations, which have been ongoing since 2003, is the U.S. demand for nuclear inspectors to be able to take samples from North Korean facilities out of the country for analysis.
The negotiations have been complicated by North Korea's refusal to acknowledge Japan as a participant over Tokyo's failure to meet its obligations under a 2007 six-party agreement to provide fuel aid to Pyongyang in exchange for the dismantling of North Korean nuclear facilities and disclosure of all information on past nuclear activities.
