"That approach didn't work previously," White House spokesman Scott McClellan said. "North Korea violated their agreement."

He said Bush believed it was "important to work through the multilateral six-party talks to bring about a peaceful diplomatic resolution to this concern."

North Korean leader Kim Jong-Il's visit to China last week appeared to have given greater momentum to the talks between China, South Korea, Japan, the United States, North Korea and Russia to resolve the nuclear issue.

Pyongyang earlier announced it would attend May 12 talks in Beijing aimed at setting up a fresh round of the six-nation negotiations by the end of June.

A North Korean foreign ministry spokesman had said Pyongyang wanted to discuss compensation for freezing its nuclear programs at the working group meeting.

John Kerry, Bush's presumptive rival in the November presidential elections, charged Wednesday that the incumbent had failed in his policy on North Korea.

Kerry wants direct talks with Pyongyang on a range of issues, not only the nuclear question.

But McClellan, citing North Korea's broken promise, rejected any notion that Bush was willing to bargain on compensations for North Korea and open a direct dialogue with North Korea.

He stressed that the nuclear crisis in the Korean peninsula "is a very serious concern of ours.

"It's a very serious concern for countries in the region. And that's why we're working together with China and South Korea and Japan and others to bring about a peaceful resolution."

The nuclear impasse erupted in October 2002 when Washington said the Stalinist state had not kept its part of the bargain by breaking a 1994 nuclear freeze and launching a secret nuclear weapons program.

The United States said it had learned "conclusively" that North Korea was pursuing a covert nuclear weapons program based not on plutonium but on uranium enrichment.

Two rounds of six-way talks hosted by China have failed to narrow key differences on how to end the 18-month-old standoff.

Washington is demanding the complete, verifiable, and irreversible dismantling of North Korea's nuclear programs, both plutonium and enriched uranium, before it will offer concessions to the impoverished state.

Pyongyang denies it is running a uranium scheme, and says it is prepared to freeze its plutonium facilities in return for simultaneous rewards from the United States.

McClellan said the United States wanted to see progress in the working group talks.

"North Korea needs to dismantle its nuclear program in a verifiable and irreversible way, and we want to see progress toward that in these talks.

"And we're going in these talks without any set preconditions. That's the shared goal of all the countries that are involved in these multiparty talks," he said.

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