North Korea, also called Democratic People's Republic of Korea (DPRK), said it hoped the talks would create "a positive result" and narrow the gap between Pyongyang and Washington.
North Korea's top negotiator, Deputy Foreign Minister Kim Gye-gwan said political will at this round "would serve as a basis for narrowing down the existing differences of position and opinions between the DPRK and the United States and break the current impasse".
Kim eschewed North Korea's traditional anti-US rhetoric, although a day earlier the Foreign Ministry warned the US not to accuse it of pursuing a uranium weapons programme.
The US stood fast, calling for the irreversible, verifiable dismantling of North Korea's plutonium and uranium weapons programmes and repeating that it did not intend to attack a country it branded part of an "axis of evil" with Iran and pre-war Iraq.
After half a year of shuttle diplomacy, delegates from North and South Korea, the US, China, Russia and Japan shook hands before taking their places at a hexagonal table in a guarded guesthouse in Beijing for the second such meeting brokered by China.
"The United States seeks the complete, verifiable and irreversible dismantlement of all the DPRK's (North Korea's) nuclear programmes, both plutonium and uranium-based," Assistant Secretary of State James Kelly said.
"The United States has no intention of invading or attacking the DPRK"
assistant secretary of state, USA
In a move to reassure Pyongyang, which has demanded security guarantees from the US in the form of a non-aggression pact, Kelly said North Korea had no need for
"The United States has no intention of invading or attacking the DPRK," he said.
The nuclear crisis erupted in October 2002 when US officials said North Korea admitted to a covert programme to enrich uranium for nuclear weapons.
Pyongyang has since denied such a scheme, but it has offered to freeze a plutonium-based programme that it reactivated when it pulled out of the nuclear Non-Proliferation Treaty last year.
However, it warned on Tuesday that any attempt to raise the "purely fictitious" uranium issue would only prolong the crisis.
US officials and arms control experts say it would be meaningless to exclude the uranium programme from efforts to disarm North Korea because, unlike the reactor-centred production of plutonium at Yongbyon, uranium enrichment can be hidden.