Echoing public and private comments from French, German and British officials, ElBaradei said the only way to end the crisis and avoid confrontation was for the Bush administration to get involved in the talks between the three countries and Iran.
"I don't think the Iranian issue will be resolved without the United States putting fully its weight behind the Europeans," he said.
Mohamed ElBaradei, head of the International Atomic Energy Agency, said recent evidence does not substantiate claims that Iran is working toward a nuclear bomb.
"We have been very active diplomatically, including working with the IAEA, on both Iran and North Korea," a senior Bush administration official said, speaking on condition of anonymity because he had not seen ElBaradei's full comments. "It is clear that these nations need to take the IAEA more seriously and need to work toward that goal."
The official added that the IAEA's own reports demonstrate an "established pattern" over decades of Iran using peaceful nuclear programs to move toward developing nuclear weapons. "It is not a matter of finding a bomb in a given week," he said.
ElBaradei backed the idea of a comprehensive deal between the West and Iran that would address nuclear power, regional security, terrorism and Iranian recognition of Israel. Iran's negotiations with the Europeans touch on some of those issues, and diplomats have signaled that Tehran would be willing to go further if the United States took part.
Over the past four years ElBaradei has been juggling investigations in Iraq, Iran, North Korea, Libya and Pakistan. Of those countries, he said North Korea was "the greatest security challenge" faced by the world. "I am very concerned about the North Korea dialogue right now. . . . The six-party talks never really took off," he said.
At the last such meeting, the United States said it would support a South Korean and Japanese proposal to provide energy assistance if North Korea agreed to dismantle its nuclear programs. But the United States said it would not consider providing direct concessions until U.S. intelligence had verified that North Korea had fully disclosed the extent of its nuclear activities.
The North has not officially responded to the offers, but throughout the last two years, has sought to win direct benefits from the United States as a condition of ending its nuclear programs.
Last week, North Korea announced that it had built nuclear weapons and was suspending participation in the talks.
ElBaradei said the agency had no way to verify the weapons claim. IAEA inspectors were expelled from North Korea at the end of 2002.
But he called the claim a sign that North Korea was feeling helpless and ignored. "This is their trump card, and they will try to squeeze every drop of blood out of it," he said. He urged a strategy aimed at coaxing North Korea back into accepting IAEA inspections. "The sooner, the better," he said.
Kessler reported from Washington.