"I'm not aware of a new number," he said in response to a Washington Post account, which cited officials preparing a report on the matter to be completed within a month.

"I have not been given any such information by the intelligence community," he told reporters in Berlin.

Powell, who was in the German capital to attend an international anti-Semitism conference, reiterated Washington's position that Pyongyang should use six-way talks to come to an agreement to disarm.

"North Korea needs to come to the realization that nuclear weapons will not serve it any particular useful purpose," he said.

"What they have to do is engage seriously in the six-party talks so that we can achieve complete, verifiable, irreversible dismantlement of their nuclear weapons systems. The United States will not be pressured or pushed into any other outcome."

Up to now, the United States estimated that Pyongyang had developed enough weapons grade material at the nuclear facilities it reopened last year to make possibly two nuclear devices.

Two rounds of six-way talks hosted by China have failed to narrow key differences on how to end the stand-off.

New talks -- which bring together the two Koreas, the United States, China, Russia and Japan -- are to open in Beijing by the end of June.

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