Congressional investigators say some foreign intelligence analysts believe U.S. intelligence is underestimating Iran's progress toward designing a nuclear warhead before Tehran halted its program in 2003.
The foreign analysts believe that Iran ended its work because it had made sufficient progress, not because of international pressure, as the 2007 U.S. national intelligence assessment concluded.
The report by the Senate Foreign Relations Committee did not identify its sources, referring only to "intelligence analysts and nuclear experts working for foreign governments." It says some research was conducted in Israel, which has been publicly critical of the 2007 U.S. assessment.
The foreign analysts believe "intelligence indicates Iran had produced a suitable design, manufactured some components and conducted enough successful explosives tests to put the project on the shelf until it manufactured the fissile material required for several weapons," the report says.
The revelations by the committee, headed by Sen. John Kerry, D-Mass., come as President Barack Obama is promising direct engagement with Iran and seeking diplomatic openings. The report backs the Obama administration's approach but recommends balancing new openings with continued pressure.
In an introduction to the report, Kerry wrote that a major obstacle the administration will have to negotiate "is the suspicion surrounding Iran's nuclear program."
The report also provides new details on Iran's nuclear program and its attempts to thwart U.N. inspectors. Citing an unidentified official at the U.N. International Atomic Energy Agency, it says that Iran reneged at the last minute on an agreement last summer to allow inspectors to visit suspected nuclear workshops.
"Unclassified U.S. intelligence assessments and staff interviews with government officials and diplomats in Washington and foreign countries leave little doubt that Iran has the technological and industrial capacity to eventually develop an atomic bomb," the report concludes.
The report examines material provided to the IAEA by U.S. intelligence from a laptop computer that reportedly was smuggled out of Iran. In 2005, U.S. intelligence assessed that information as indicating that Tehran had been working on details of nuclear weapons, including missile trajectories and ideal altitudes for exploding warheads.
The material on the laptop also included videos of what intelligence officials believe were secret nuclear laboratories in Iran. Iran has accused the United States of fabricating the material. The report says that U.N. and non-U.S. intelligence officials told committee investigators that they could not rule out an intelligence ruse, but they say other documents corroborate some of the information from the laptop.
The report says that officials the committee talked to concluded the documents "appear to be authentic, right down to the names, addresses and telephone numbers of the workshops."
Iran insists that its nuclear program is purely to provide electric power, not weapons.
The report also reveals that Iran agreed to allow the IAEA to inspect the workshops last August. After a senior IAEA official arrived in Tehran, however, the agency was told that the government had changed its mind.
The report concludes that Iran continues to use front companies to look for important components on the black market. It says that it is particularly eager to obtain carbon fibers and specialized metals for use in advanced centrifuges.