"North Korea expressed its intention to declare and disable [all its nuclear facilities] within the shortest possible period, even within five or six months, or by the end of the year,'' Chun said.
He added that Kim also said during a one-on-one meeting in Beijing that North Korea was "willing to declare all its nuclear programmes without omitting a single one".
"The point of what North Korea said yesterday was that it would not drag its feet or make unreasonable demands in carrying out its obligations," he said.
"North Korea has only one card in hand and that is its nuclear programme
Rahy, Tehran, Iran
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The delegates now want to emphasise the importance of sticking to a disarmament time-table in Thursday's talks.
Christopher Hill, the chief US negotiator, said: "So, we did okay in the first phase with the understanding that we missed just about every deadline and we don't want to do that anymore.
"So, I guess we have to be careful about deadlines. But if you don't have deadlines you will never get stuff done. So we have to balance that."
Hill said there had to be a follow-on "and probably an even more important" phase.
"That's the actual abandonment of the fissile material and explosive devices on the [North Korea] side and that's very important."'Total disclosure'
By disabling its nuclear facilities, North Korea would lose its ability to make more atomic bombs, going beyond achievements at any previous arms negotiations.
North Korea's pledge of total disclosure is key because in 2002 the US accused it of having a uranium enrichment programme, which Pyongyang has denied.
The US says a declaration must include the bombs already built in addition to any radioactive material North Korea might have.
Pyongyang had previously shut down its reactor after a 1994 deal with the US but rapidly powered it up again when the agreement fell apart in 2002, sparking the current standoff.
Pyongyang has begun receiving 50,000 tonnes of fuel oil from South Korea as compensation for the shutting down its main nuclear reactor in Yongbyon.
It will eventually receive the equivalent of a total of one million tonnes of oil for permanently disabling its nuclear facilities under a February agreement among the six parties.