The two main protagonists of the 20-month impasse were to meet in Beijing's Diaoyutai State Guest House at 0700 GMT, a South Korean diplomat said.

North Korea was also due to meet Japan, which Thursday announced for the first time its readiness to join international energy aid to Pyongyang if it freezes all its nuclear programmes before they are abolished outright.

The meetings follow the tabling on Wednesday of a seven-page US proposal aimed at dismantling the North's nuclear arsenal and ending decades of international isolation.

The offer submitted at talks also involving Russia, China, and South Korea offered a glimmer of hope that the stalemate could be broken, but it remains unclear how the unpredictable Stalinist regime will react.

North Korea has lodged its own 12-page "freeze for compensation" document.

In a sign of how delicate negotiations have become, scheduled courtesy calls by the six chief delegates to Chinese leaders Thursday afternoon were put off in favour of bilateral contacts.

Without commenting specifically on the North Korean response to the US proposal, Chinese foreign ministry spokeswoman Zhang Qiyue said "various parties have treated the plans put forward by other parties in a forward looking manner".

For its part, China called the US package "full and comprehensive".

"The plan itself shows that the meeting is progressing and that the US side hopes to see the settlement of the issue," said Zhang.

According to the Xinhua news agency, Russian delegation head Alexander Alexeyev said the meeting, scheduled to end Saturday, would not conclude "without any result".

The US plan, coordinated with North Korea's key ally, China, and US allies South Korea and Japan, is seen as more flexible than previous demands for North Korea to first completely dismantle its nuclear programmes before any aid is channeled to the impoverished state.

Under the proposal, North Korea would receive food and energy assistance and a multilateral security guarantee if it agrees to take apart its plutonium and uranium weapons programmes.

The United States would also begin direct talks about lifting its array of economic sanctions, and knocking North Korea off its list of terrorist states.

In return, the Stalinist state would have three months to provide a list of its nuclear facilities and allow monitoring.

"A good-faith action on North Korea's part would be met with a good-faith response by the other parties," White House spokesman Scott McClellan said.

It is the first significant overture to Pyongyang since US President George W. Bush took office in early 2001 and branded the North part of an "axis of evil" alongside Iran and pre-war Iraq.

It is based on the Libyan model in which Tripoli agreed to shelve its weapons of mass destruction programs last year.

China, South Korea and Japan had found the previous US stance inflexible and had been in favour of incremental rewards to Pyongyang while it dismantles its nuclear arsenal.

Its success though depends on whether North Korea is prepared to acknowledge and abandon its alleged uranium enrichment facilities.

Analysts said the US presidential elections were weighing heavily on how North Korea would respond.

"(North Korean leader) Kim Jong-il may not take the deal. He may think he can get a better deal from (US presidential candidate John) Kerry," said David Zweig, a China watcher at Hong Kong University of Science and Technology.