North Korea also struck a less confrontational tone, announcing that it wanted to work towards a nuclear-free Korean peninsula in language observers saw as a positive sign that progress could be made after a 13-month deadlock.

The US approach, just months after Washington described the secretive Stalinist state as an "outpost of tyranny", will go some way to placating the North which has long urged the US to recognise it as a legitimate government.

But the United States made no mention about normalising ties, another key demand of North Korea before it agrees to work on ways to dismantle its atomic weapons.

"We view the DPRK's sovereignty as a matter of fact. ... And we remain prepared to speak with the DPRK bilaterally in the context of these talks," chief US envoy Christopher Hill said in opening remarks.

The Democratic Peoples' Republic of Korea is North Korea's official name.

The softer line from Washington, which was instrumental in bringing North Korea back to the negotiating table, followed a rare bilateral meeting between the two sides Monday.

The two sides had another one-on-one contact Tuesday afternoon, which Hill described as "good" and "businesslike." But he predicted it would take a long time for issues to be settled.

"Everyone had the opportunity to put their issues on the table, ... but this may take a little longer than you would want and I want," he said.

Hill said the two sides also discussed a US proposal put forward last June, which required North Korea to pledge to dismantle all its plutonium and uranium weapons programs before receiving any energy and other assistance.

"I don't want to characterise their response, ... I don't want to call it positive or negative," Hill said.

Last year the North rejected the proposal, instead it wanted a step-by-step approach, fearing it could come under attack by the United States.

In his opening remarks to the talks which include South Korea, Russia, China and Japan, Hill repeated that the United States had no intention of attacking North Korea, meeting a demand for assurances of non-aggression, and offered to address concerns about aid and energy.

"All the parties have made clear we are prepared to address the DPRK's security concerns. We've made clear we're prepared to address the DPRK's energy needs," he said.

"When the DPRK makes the decision to dismantle its nuclear program permanently, fully, verifiably, other parties including my country are prepared to take corresponding measures consistent with the principle of words for words and actions for actions."

North Korea abandoned the six-party talks last year complaining of a hostile US policy, and has since claimed it already possesses nuclear weapons.

But North Korea's chief delegate said in his address that his government was "fully ready and prepared" to work on ways to rid itself of nuclear weapons.

"We think that the resuming of the talks itself is important but the fundamentally important thing is to make real progress in denuclearizing the Korean peninsula," said Kim Kye-Gwan.

"To that end, the parties concerned need to eventually remove the threat of a nuclear war from the Korean peninsula and to have a firm political will and a strategic decision to realize the denuclearization of the Korean peninsula."

Last week it called for a peace treaty with the United States to replace an armistice reached at the end of the Korean War in 1953, saying this could persuade it to drop its nuclear program.

The North's close ally China said the "atmosphere has improved" from the earlier rounds while South Korean officials called Tuesday's negotiations "more polite and civilized than before".

A North Korean source quoted by Russia's Interfax news agency however cautioned that "it's clear that there are still serious disagreements on ways of resolving the denuclearization problem".

This time South Korea has offered to provide the North with 500,000 tonnes of rice and route some 2,000 megawatts of electricity to the isolated regime.

The standoff was sparked in October 2002 when Washington accused the North of operating a nuclear weapons program based on enriched uranium in violation of a 1994 agreement.

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