Twenty-one commanders of the Iranian Revolutionary Guard Corps are the top scientists running Iran's secret nuclear weapons program, says the man who exposed Iran's nuclear weapons program in 2002.

On top of that, the U.S. National Intelligence Estimate published last week saying Tehran shut down its weaponization program in 2003 failed to mention that the program restarted in mid-2004, said Alireza Jafarzadeh, an Iranian dissident and president of Strategic Policy Consulting.

The scientists working on the alleged civilian nuclear centrifuge program are IGRC commanders, said Jafarzadeh, who was providing a list of names to the press on Tuesday. But their intention is not a nuclear energy source for civilians.

"It's the IRGC that is basically controlling the whole thing, dominating the whole thing," Jafarzadeh told FOXNews.com. "They are running the show. They have a number of sites controlled by the IRGC that has been off-limits to the IAEA (International Atomic Energy Agency) and inspectors, including a military university known as Imam Hossein University. ... That site has not been inspected. They have perhaps the most advanced nuclear research and development center in that university."

Jafarzadeh said the 2003 decision to stop the weaponization program, which was operating in Lavizan-Shian, a posh northeast district of Tehran, was not Iran's own. The site had been exposed by the opposition, the National Council of Resistance on Iran, in April 2003 after revelations of several other nuclear sites that could be portrayed as dual purpose facilities. Lavizan-Shian could not, he said.

"The regime knew that this is not the site that they can invite the IAEA ... this site was heavily involved in militarization of the program," Jafarzadeh said. "They were doing all kinds of activities that were not justifiable. So they decided before the IAEA gets in — and it usually takes four to six months before they can go through the process and get in — use the time and try to basically destroy this whole facility, and that's what they did."

Jafarzadeh said the Iranians razed the buildings, removed the soil, cut down the trees and allowed the IAEA to inspect the Lavizan-Shian site, which had been turned into a park by June 2004. He noted that the regime acted as if it had succumbed to municipal pressure to open a park with basketball and tennis courts and that is why the area had been flattened.

Jafarzadeh said that "in a way it's correct for the NIE to say that in late 2003 the weaponization of the program was stopped, and they said it was due to international pressure. But they failed to say that it restarted in 2004" in a location called Lavizan 2, he said.

Lavizan 2 "has never been inspected by the IAEA," Jafarzadeh added.

Jafarzadeh's comments preceded a call by President Bush on Tuesday for Iran to explain why it had a secretive nuclear weapons program, and warned that any such efforts must not be allowed to flourish "for the sake of world peace." The NIE noted that Iran continues to enrich uranium, which can be turned toward making a weapon if the country wanted to pursue that end.

"Iran is dangerous," Bush said after an Oval Office meeting with Italian President Giorgio Napolitano. "We believe Iran had a secret military weapons program, and Iran must explain to the world why they had such a program. ... Iran has an obligation to explain to the IAEA why they hid this program from them.

"Iran is dangerous, and they'll be even more dangerous if they learn how to enrich uranium," Bush said. "So I look forward to working with the president," Bush said, referring to Napolitano, the Italian leader, "to explain our strategy and to figure out ways we can work together to prevent this from happening for the sake of world peace."

Bush's remarks followed a press conference by Iranian President Mahmoud Ahmadinejad praising the latest NIE as "a step forward" for U.S.-Iranian relations, and suggesting an "entirely different" situation could be created between the United States and Iran if more steps like the report followed.

"We consider this measure by the U.S. government a positive step. It is a step forward," Ahmadinejad said. "If one or two other steps are taken, the issues we have in front of us will be entirely different and will lose their complexity, and the way will be open for the resolution of basic issues in the region and in dealings between the two sides."

But Jafarzadeh said Iran can't be trusted, and suggested that the U.S. intelligence community was duped by plants placed by the Islamic regime to provide disinformation about its programs.

"There are two extremes" for explaining the NIE's reversal from 2005, the last report on Iran's weapons program, said Jafarzadeh. One, career types in the Bush administration issued the analysis for purely political reasons, like wanting to hurt the administration, keeping rapprochement open or removing the military option from the table.

"The other one is it's not political at all, it's just basically deceit ... by the regime — that they managed to get so-called 'defectors' to make the Americans and the intelligence community believe that what happened in late 2003 was actually a decision to totally halt the program. They sold it that way to the Americans. ... They are like a fox, the animal is famous in Iran for being tricky. So it's very possible that it was well-orchestrated by Tehran, and they succeeded in at least getting that sentence from the intelligence community in the report."

In August 2002, Jafarzadeh, then-spokesman for the National Council of Resistance on Iran, revealed the name of the Natanz nuclear site, which the Iranian government since has acknowledged and which is subject to IAEA inspections.

Because of its integral relationship to Mujahedin-e Khalq, or MEK, an Iranian resistance group, NCRI is deemed a terrorist organization in the United States, despite calls by several members of Congress to remove its designation from the State Department list.

NCRI also is on the British and European Union terrorist list, placed there at the start of the decade by Western countries trying to improve relations with Tehran. Last week a British judge ordered NCRI to be removed from the British list. Pressure also is on the EU to drop MEK.

Nonetheless, NCRI and Jafarzadeh, working independently, have concluded that Iran did shut down its nuclear weapons program in 2003 but restarted it a year later, moving and hiding equipment to a variety of sites.

Mohammad Mohaddessin, NCRI's foreign affairs chief, told The Wall Street Journal in Tuesday's editions that some of the equipment was moved to another military compound known as the Center for Readiness and Advanced Technology, to Malek-Ashtar University Isfahan and to a defense ministry hospital in Tehran.

Click here to read The Wall Street Journal report (subscription required).

The facility was broken into 11 fields of research, including projects to develop a nuclear trigger and shape weapons-grade uranium into a warhead, the paper reported.

"They scattered the weaponization program to other locations and restarted in 2004," Mohaddessin 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."