"Well I really think that North Korea has taken a great positive step... Bravo North Korea"
andrew, Kampala, Uganda
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But no deadline was agreed upon during the three-day talks that involve China, the two Koreas, the United States, Japan and Russia.
The six nations agreed in September 2005 to discuss furnishing North Korea with light-water reactors "at an appropriate time," with Washington insisting that Pyongyang must first disable all its current nuclear programmes.
Kim accused Japan of causing a political crisis that could lead to "disaster".
"They [Japan] are creating a political crisis worse than the financial sanctions, a crisis that infringes on our national sovereignty."
He said he expressed his concerns to Kenichiro Sasae, his Japanese counterpart, on Thursday during a rare bilateral meeting in Beijing.
"I warned that if they take one more step forward a disaster would come," Kim said.
He refused to elaborate, but his comments came amid strong criticism from North Korea over Japan's recent forced auction of the headquarters of Chongryon, the North Korean-focused General Association of Korean Residents in Japan.
Despite his strong words on Japan, Kim said this week's six-party talks had been held in a "sincere, constructive and business-like" manner.
The talks were the first since March, when negotiations broke down over US financial sanctions imposed on Pyongyang who was accused of money-laundering and counterfeiting.
Talks aimed at curbing North Korea's nuclear ambitions began in 2003 and in October last year, the country went ahead with its first atomic test.