North Korea has persistently indicated it is not interested in attending the fourth round of the six-party talks, seen as the "last window" to ending the nuclear standoff in the Korean peninsula before the US presidential elections in November.

"It doesn't seem probable there will be another round by the September time frame and therefore with proximity to elections it doesn't seem likely also for another round of talks this year," said Fred Carriere, the executive director of The Korea Society, based in New York.

"So, if there is no momentum in the talks up to next year, it raises the bigger question of whether the six party talks have indeed failed," said Carriere, an experienced Korea hand.

Aside from North Korea and the United States, the talks launched about a year ago include host China, Russia, South Korea and Japan.

The unpredictable North Korea has so far refused to commit a September date for the talks, citing various reasons -- uncertainty ahead of the US elections, South Korea's recent admission of involvement in illicit nuclear activities and rejection of a Washington aid-for-disarmament offer.

Russia, and North Korea's biggest ally China have indicated they can do little to prod Pyongyang to return to the negotiating table.

"Russia of course would like to see this round take place at the end of September as agreed at the third round in Beijing. But for many different reasons, this is not working out," Russian deputy foreign minister Alexander Alexeyev said after meeting Tuesday with South Korean counterpart Lee Soo-Hyuck.

Chinese foreign ministry spokesman Kong Quan also Tuesday said "the sky won't fall down" if the talks fail to take place before the end of the month.

But the US State Department is unmoved by the discouraging words.

"We would expect the North Koreans to live up to (their) commitment (to attend the talks) but it does look like that they've been stalling, and at this point they haven't agreed yet," said department spokesman Richard Boucher.

Asked whether he would conclude then that no talks would be held this month, he said: "I'll conclude that on September 31."

"It seems fairly unlikely at this point" that the talks would be held September, said Richard Bush, director of Northeast Asian studies at Brookings Institution. "It appears that North Korea is being difficult as usual."

The talks are useful but they "seem like getting squeezed" by schedule difficulties, including the UN General Assembly and China's ruling Communist Party plenary session slated this month, he said.

He said that if Bush were reelected in November, he could still pull off a resumption of the talks by the end of the year and "hit the ball into the North Korean court and get them to explain why they cannot move forward."

At the last round of talks in June, the United States offered Pyongyang three months to shut down and seal its nuclear weapons facilities in return for economic and diplomatic rewards and multilateral security guarantees.

North Korea refused the offer, saying it was not substantial and lacked sincerity.

The offer was seen as the first significant overture to Pyongyang since Bush took office in early 2001 and branded the North part of an "axis of evil" alongside Iran and pre-war Iraq.

A working group meeting ahead of the plenary six-party talks was supposed to have been held earlier this month at which North Korea was to have officially responded to the US offer. Pyongyang also refused to attend that meeting.

Carriere said that if the talks this month were scrapped, the prospect of them continuing at all was slim if Bush's Democratic party rival John Kerry won in elections.

Kerry had said he preferred bilateral talks with North Korea to resolve the crisis unlike Bush's preference for multilateral discussions.

"Even if Bush won in the November elections, it will be too soon for the talks to resume in December," Carriere said. "With such a long gap, momentum is lost."

The nuclear stand-off flared in October 2002 when the United States accused North Korea of operating a nuclear weapons programme based on enriched uranium, violating a 1994 agreement.

Pyongyang has denied running the uranium-based program but has restarted its plutonium program.

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