Optimism was waning in Beijing, where six-party members on Monday shifted the debate from how to disarm North Korea to a new topic — whether or not to extend the negotiations with Pyongyang.

It was a last-ditch effort for more time so envoys could again try to convince the Communist country to abandon its nuclear program, with North Korea being rewarded with oil and energy imports from neighbouring countries if it does so.

But the lingering disagreements among the six countries in the summit — Russia, China, Japan, the two Koreas and the U.S. — appeared to snuff out the sense of hope with which the sessions first opened five days earlier.

A decision to extend negotiations could be seen as an indication the other five parties believe a deal is within grasp and that North Korea is taking the matter seriously. A reporter with the Christian Science Monitor told CBC News a South Korean official hinted a deal could be struck by Monday night.

Speculation is that the deadlock is embedded in the details, as reports have indicated Pyongyang is asking for $600 million worth of oil every year, as well as two million kilowatts of electricity from its neighbours. The other five countries believe that's too tall an order.

A South Korean official, speaking on condition of anonymity, told the Associated Press on Monday "the talks are expected to continue tomorrow," meaning an extension of the summit by at least one day.

Russia not backing extension: report

An official with Japan's Foreign Ministry, also speaking on condition of anonymity, said "Russia has said 'no' to extending the talks" and South Korea wants them to continue, but "Japan is assessing the situation."

Before entering Monday's final session in Beijing, lead American negotiator Christopher Hill told reporters "it's up to the North Koreans."

"We have put everything on the table," said Hill, who is also the U.S. assistant secretary of state. "We have offered a way forward on a number of issues. They just need to make a decision."

Japan's Minister of State Fukushiro Nukaga told reporters Pyongyang was prepared to close its main nuclear reactor and submit to weapons inspectors, but could not agree with the other parties on how much energy aid it should receive in return.

The current round of talks resumed Thursday after more than three years of stalled negotiations, with North Korea showing a willingness to compromise. But envoys have not been able to move past the energy issue.

If North Korea rejects the current proposal, the talks could be permanently doomed.

"There's a certain life cycle to these negotiations," Hill acknowledged.

But he added, "I don't want to predict that this is the last chance."

With files from the Associated Press