North Korean nuclear talks went into a second day on Friday after a "good start", with envoys looking to secure agreement on how to verify Pyongyang is telling the truth about its atomic programmes.
US negotiator Christopher Hill was cautiously optimistic following a marathon first day that saw delegates from the six nations involved hold their first meeting in nine months.
"All in all I think there is a good start to the process," Hill told reporters after midnight.
"But I think the effort to negotiate the actual verification protocol will be very important."
The six-nation talks -- which involve China as host, the two Koreas, the United States, Japan and Russia -- began in 2003 with the aim of persuading North Korea to abandon its nuclear programmes.
But they had not been held since October, as the other parties involved waited for North Korea to give an account of the nuclear programmes it had spent decades developing.
The declaration was a key part of the six-nation disarmament accord reached last year, under which the North agreed to abandon its nuclear programmes in exchange for a rich array of diplomatic incentives and economic aid.
North Korea finally gave its declaration last month, and the US immediately responded by easing some trade sanctions and beginning the process of taking Kim Jong-Il's regime off its list of state sponsors of terrorism.
Those developments paved the way for the current round of talks, where a main focus is working out a way to verify North Korea's nuclear declaration.
"(We are) basically discussing, for example, the fact that verification needs include site visits... documents and interviews," Hill said.
He said talks on Friday aimed to better define the verification process.
"The key thing will be ... when the nuclear working group meets, to actually work out the actual protocol."
Hill said the other main issue on the agenda on Friday would be the delivery of energy aid to North Korea.
Under the disarmament accord, the North should get energy aid equivalent to one million tons of fuel oil in return for disabling its main plutonium-producing Yongbyon facility and documenting its nuclear activities.
The North shut down its Yongbyon reactor -- which produced the material for the nation's historic atom bomb test in 2006 -- in July last year.
It then began disabling the plant under the supervision of US inspectors in November, and last month blew up the cooling tower at Yongbyon in a gesture intended to demonstrate its commitment to disarmament.
However a North Korean foreign ministry spokesman said in the lead-up to this week's talks that while 80 percent of the Yongbyon facility had been disabled, only 40 percent of the promised energy aid has been delivered.
"We'll be hoping to take on the issue of economic and energy assistance for the DPRK (North Korea)," Hill said.
After the first day of talks, South Korean chief envoy Kim Sook cautioned against any quick breakthrough.
"We have a situation which requires somewhat more time and additional efforts," he said.
The third and final phase of the disarmament deal calls for the North to permanently dismantle its atomic plants and hand over all nuclear material and weaponry.
In return, it would get more energy aid, restored diplomatic ties with the United States and Japan, and a formal peace treaty that would officially end the 1950-53 Korean war.
