Principal Deputy Director of National Intelligence Donald Kerr said, however, that the National Intelligence Estimate on Iran also reflects significant concerns over Iran's intentions, and that these have been overlooked in public debate.
US intelligence officials have spent considerable effort trying to emphasize those concerns since an unclassified version of the document was released in December, Kerr told a think-tank audience.
"Until we have new data, new facts, we're not going to change the basic NIE, the classified version," Kerr told a dinner sponsored by the Washington Institute for Near East Policy.
"We of course are working every day to either find more facts, new facts, or those that might support where we are today," he said.
The estimate said Iran had stopped its development of a nuclear device in 2003 – a change from previous findings – but continued both efforts to enrich uranium that can be used for nuclear weapons and its ballistic-missile program.
The disclosure that Iran had stopped device development sparked an international political storm. It slowed what critics had called a hasty rush led by the United States to confront Iran over its nuclear aims, including possible use of force.
Iranian President Mahmoud Ahmadinejad, who has maintained Iran's nuclear program is peaceful, declared victory.
Conservative critics accused US intelligence of understating the threat and undermining President George W. Bush's get-tough policy on Iran.
"In the end we had the perfect storm. Across the entire political spectrum we had made somebody mad," Kerr said. "We didn't do the job we should have in expressing points we were trying to make."
Kerr said he has since sought to emphasize the critical importance of Iran's nuclear material and missile-development programs, which have continued.
"Once you have fissile material in sufficient quantity we're not talking about a great long period of time before an effective weapons capability might exist," he said.