The two Koreas, the United States, Japan, China and Russia have agreed to start a working group meeting on May 12, Yonhap news agency said, adding an announcement could be made soon.

Ning Fukui, Beijing's special envoy for Korean Peninsula affairs, called for a "flexible" approach toward the 18-month-old nuclear stand-off after arriving in South Korea for a two-day visit.

"At working group talks, participants should have in-depth talks to seek ways of defusing tensions over the North Korean nuclear issue," he said, without confirming the new round of discussions.

"We hope the participants will be more flexible and take a realistic approach so that progress can be made," the Chinese official told reporters. He is expected to head the Chinese team to the working group meeting.

A row over North Korea's nuclear program has been deadlocked since October 2002, when Washington said the Stalinist state had broken a 1994 nuclear freeze by launching a secret weapons drive.

Two rounds of six-party talks hosted by China to defuse the crisis have so far failed to narrow differences over the US demand and Pyongyang's denial that it was running an enriched-uranium program.

A new round of talks is expected before the end of June. Working parties are to be set up to resolve contentious issues.

Yonhap said the date for working group talks was fixed when North Korean leader Kim Jong-Il visited China last week.

The issue attracted new attention Thursday after the Washington Post newspaper reported that the United States believed North Korea could have at least eight nuclear bombs.

The estimate is based on a detailed analysis of plutonium products found on clothing worn by an unofficial US delegation which visited North Korean nuclear facilities several months ago, it said.

Up to now, Washington estimates, Pyongyang has developed enough weapons grade material at the nuclear facilities it reopened last year to make possibly two devices.

Last year, Pyongyang claimed it had finished reprocessing around 8,000 spent nuclear fuel rods, which experts believe can give it enough plutonium to make up to six more nuclear bombs.

The Post said US intelligence officials have also concluded that a separate North Korean uranium-enrichment program would be operational by 2007, with a capacity to produce as many as six additional nuclear weapons a year.

Other US officials downplayed but did not deny the reports over the possible size of North Korea's nuclear arsenal.

"I'm not aware of a new number," Secretary of State Colin Powell said in Berlin. He reiterated Washington's position that Pyongyang should use six-way talks to come to an agreement to disarm.

South Korean Unification Minister Jeong Se-Hyun downplayed the report as "one of allegations."

"South Korea and the United States share information over the nuclear issue and there are little differences on it," he said.

Jeong said he would call for a positive reponse from North Korea over the impasse at inter-Korean minister-level talks to be held next week in Pyongayng.

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