But both North Korea and the United States warned against reading too much into the first day of talks and "counting chickens before they hatch."

A diplomatic source close to the six-party talks said the draft prepared by China stated that North Korea would "suspend, shut down and seal" nuclear facilities at the Yongbyon plant within about two months in return for energy and economic aid.

The fresh momentum in the talks between the two Koreas, China, the United States, Japan and Russia came after the US and North Korean negotiators held path-breaking two-way talks in Berlin last month.

The Berlin meeting cooled tension that had boiled after Pyongyang staged its first nuclear test blast last October and the United Nations responded with sanctions.

Envoys to the talks voiced hope that North Korea was now ready to restrict its nuclear ambitions after over three years of stop-start negotiations.

"There is a realisation that the first step we're looking at is a big first step, so to some extent it's going to require a little bit of a jump for them," the chief US negotiator, Assistant Secretary of State Christopher Hill, told reporters after meeting the North Korean delegation.

Echoing a comment by US Secretary of State Condoleezza Rice on Thursday, he said: "I think we can be cautiously optimistic but don't want to count our chickens before they hatch."