"The six countries have agreed that the working group's meeting will open on May 12 in Beijing," Deputy Foreign Minister Lee Soo-Hyuck, Seoul's chief delegate to the six-way talks, told journalists.

"The meeting is open-ended, without a closing date fixed."

The announcement was made possible only after North Korea agreed to the opening date for the "preparatory meeting" to help the six-nation talks go smoothly, Lee said.

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 -- bringing together the two Koreas, the United States, Japan, China and Russia -- have 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.

The forthcoming working-group talks will tackle "the complete, verifiable and irreversible dismantling (CVID) of North Korea's nuclear programs and the CVID-based nuclear freezing for a peaceful settlement," Lee said.

Ning Fukui, Beijing's special envoy for Korean Peninsula affairs, called for a "flexible" approach toward the 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.

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

The date for the working group meeting was fixed after a visit by North Korean leader Kim Jong-Il to China last week.

The issue attracted new attention Thursday after the Washington Post newspaper reported 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.

But Seoul dismissed the news report as groundless.

"After checking the Washington Post report out with the US government, we learned that it was groundless information. The Washington Post also clarified it was guesswork," Deputy Foreign Minister Lee 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 concluded that a separate North Korean uranium-enrichment program would be operational by 2007, with 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."

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

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