North Korea's envoy at talks on the country's nuclear programme has said it should be given light-water reactors as reward for axing its current programme.
Mr Kim said Pyongyang should be rewarded
Such reactors cannot easily be used for making weapons-grade material, but correspondents say the demand may cause problems for the six-party talks.
North Korea's negotiator, Kim Kye-gwan, made his remarks as he left Beijing.
Pyongyang was offered similar reactors in a deal with the US in 1994, but the agreement later fell through.
Mr Kim said Pyongyang should be given a light-water reactor in exchange for dismantling its Yongbyon nuclear plant.
But he acknowledged that the other countries involved in the nuclear deal did not seem ready to oblige.
Negotiators wanted Pyongyang, which has already closed its main nuclear site, to agree to a timetable for disclosing and disabling all its nuclear facilities.
North Korea has turned its back on nuclear treaties
Envoys from the six countries involved in the talks will meet again in September, Chinese envoy Wu Dawei said.
Washington has insisted discussions on the supply of light-water reactors would only take place after the North Koreans rejoined the Nuclear Non-Proliferation Treaty, which Pyongyang quit in early 2003.
"In order to set a deadline, we have to clearly define he obligations of each side and sequence corresponding actions," Mr Kim was quoted by Associated Press news agency.
"Time was not enough and preparations were not enough this time."
The latest meeting of the two Koreas, the US, China, Japan and Russia concludes the first phase of a landmark deal agreed last February.
In the past week, Pyongyang has fulfilled its pledge to shut the Yongbyon reactor, and has begun to receive the 50,000 tons of fuel oil it was promised in return.
A total of one million tons of energy aid has been promised to North Korea if it fulfils the second phase, by disabling its nuclear facilities and declaring its nuclear secrets.