The claim, to be made public today by the National Council for Resistance in Iran, joins a broad pushback by conservative hawks who say the U.S. analysis has wrongly given the impression that Iran's nuclear-fuel program doesn't present an urgent threat.
In recent days, Republican lawmakers have called for a review of the process that created the U.S. National Intelligence Estimate, a nonclassified version of which was released last week. Senior U.S. officials have been consulting with allies in Israel and Europe to explain why the estimate differed so drastically from previous assessments.
A former U.S. intelligence official who works closely with the White House on Iran said that all the intelligence related to the NIE was being reassessed and that information coming from sources such as the NCRI would be included. "You have to take seriously what they say, but you also have to realize that they have gotten things wrong," the official said.
Representatives of the National Security Council and the Office of the Director of National Intelligence both said they wouldn't speculate on how any new intelligence on Iran may be utilized. "We stand by the NIE assessment, which is the consensus view of all our intelligence agencies," said Ross Feinstein, a DNI spokesman.
The NCRI is the political wing of the Mujahedin e-Khalq, a group that still has as many as 4,000 members in a disarmed military camp just inside Iraq's border with Iran. The MEK has its roots as a Marxist-Islamist body that fought to overthrow the Shah and has been seeking to overthrow the current government since the mid-1980s. The U.S. and the European Union list both the NCRI and Mujahedin e-Khalq as terrorist organizations. The NCRI has had a mixed record in the accuracy of its claims concerning Iran's nuclear program.
U.S. intelligence officials have declined to comment on what role the NCRI or other Iranian dissident groups may have played in developing the new intelligence estimate. The NCRI first identified Iran's covert nuclear-fuel facilities in 2002, and the White House and State Department have credited the group with helping to expose the program.
The intelligence estimate by 16 U.S. government agencies concluded with "high confidence" that Iran shut its weaponization program in 2003, and with "moderate confidence" that it has remained frozen since. Diplomats say that because the report makes the need for action seem less urgent, it is likely to be harder for the U.S. and European Union to secure international support for tougher sanctions against Iran, aimed at pressuring it to suspend its nuclear-fuel program, which can be used for civilian or military purposes.
According to the NCRI, Iran's Supreme National Security Council decided to shut down its most important center for nuclear-weapons research in eastern Tehran, called Lavisan-Shian, in August 2003.
The NCRI, which claims to have intelligence sources inside Iran, said Lavisan was broken into 11 fields of research, including development of a nuclear trigger and of the technology to shape weapons-grade uranium into a warhead. But at the same meeting, the council decided to disperse pieces of the research to a number of locations around Iran, according to the NCRI. By the time international nuclear inspectors were allowed to get access to the Lavisan site, the buildings allegedly devoted to nuclear research had been torn down and the ground bulldozed.
"What the first part of the NIE says is right, that they halted their weaponization research in 2003," said Mohammad Mohaddessin, foreign-affairs chief for the NCRI. "But the second part, that they stopped until at least the middle of 2007, is wrong. They scattered the weaponization program to other locations and restarted in 2004."
Equipment was relocated first from Lavisan-Shian to another military compound in Tehran's Lavisan district, the Center for Readiness and Advanced Technology, Mr. Mohaddessin said. Two devices designed to measure radiation levels were moved to Malek-Ashtar University in Isfahan and to a defense ministry hospital in Tehran, he said. Other equipment was sent to other locations the NCRI hasn't been able to identify, he said.
"Their strategy was that if the IAEA found any one piece of this research program, it would be possible to justify it as civilian. But so long as it was all together, they wouldn't be able to," Mr. Mohaddessin said.
The NCRI said in a report on Iran's nuclear program in September 2005 that the Lavisan facility had been closed, setting back the regime's weaponization program by approximately one year. Mr. Mohaddessin said his group was certain no other Iranian nuclear facilities were closed in 2003.
A representative of the International Atomic Energy Agency, the United Nations nuclear watchdog in Vienna, declined to comment on the claims, but said the agency would consider seriously any NCRI information. A spokesman for the Iranian government couldn't be reached for comment.