In a statement issued outside the North Korean embassy in Beijing, foreign ministry official Park Myong-kuk expressed frustration at the US hardline stance but pledged to push on with six-nation talks in the Chinese capital.

"We had expected the US to talk differently about what kind of reciprocal measures the US and related countries will take if we freeze our nuclear program," said Park, a member of the North's delegation at the working group meeting, which entered its third day Friday despite the apparent stalemate.

"But the US repeated the same position as at the previous talks that discussions (on compensation) are possible only when we commit ourselves to CVID (complete, verifiable and irreversible dismantlement)."

He called the US demand "the kind of humiliating measure that can only be imposed on a country defeated in a war".

The row over North Korea's nuclear program has been deadlocked since October 2002, when Washington said the Stalinist state had broken a 1994 nuclear freeze by launching a secret weapons drive.

The early morning statement followed warnings by China that "major" differences remain on solving the 19-month-old standoff and underscored remarks by Russia's envoy on Thursday that chances of a breakthrough soon were remote.

Prior to the talks, Pyongyang had reiterated a demand that it be rewarded, politically and economically, for giving up its nuclear program, while the US government had ruled out any immediate pay-off.

Washington wants a clear-cut commitment from the North for a "complete, verifiable and irreversible dismantlement" before any compensation can be considered.

A key sticking point is whether North Korea should give up its entire nuclear program, or only the military part.

Washington did not have an immediate response to the North Korean statement, but reiterated its strict position.

"With respect to this issue, our policy is clear. The US objective remains the complete, verifiable and irreversible dismantlement of North Korea's nuclear program," a US embassy spokeswoman said, citing a statement from Washington.

In Seoul, South Korean Foreign Minister Ban Ki-Moon voiced optimism that a solution could be found, but said Pyongyang must take the lead.

"North Korea should completely dismantle all nuclear programs including those based on plutonium and highly enriched uranium. This will be the way to guarantee its national security and economic prosperity," he told the Asia Society.

"We anticipate that through the working group we could ... eventually foster an atmosphere to reach a peaceful resolution of the North Korea nuclear issue."

No closing date has been set for the working-level talks, which are the first since a second round of high-level six-party meetings ended inconclusively in Beijing in late February.

They are aimed at setting a date for the third round of six-party talks, expected before the end of June.

Also taking part in the negotiations is China, South Korea, Russia and Japan.

While there has been widespread speculation that the United States and North Korea will hold bilateral meetings during the working level talks, they have yet to happen, according to the US embassy spokeswoman.

US newspapers, meanwhile, said North Korea has proposed a peace treaty to be signed by Seoul, Pyongyang and Washington as a means to resolve the nuclear issue, in an apparent sign of Pyongyang's growing frustration with the Beijing negotiations.

The US spokeswoman said the issue had not been raised at this week's talks.

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