The International Atomic Energy Agency's (IAEA) latest report says that Iran "is working on research and development of nuclear weapons in a very systematic way" but falls short of confirming that Iran actually has such weapons. Mark Hibbs, a leading expert on nuclear development, says "the impression you have is that all of these things together look like a nuclear weapons program. That's of great concern." He says the IAEA indicates that the nuclear program in Iran is not run solely by civilians as Iran has contended, but that "there is a complex interaction between the military and the civilian organizations that are responsible for nuclear power development."

What's your analysis of the IAEA's latest report on Iran's nuclear program?

The report contains a very detailed compendium of all the activities that the IAEA has identified that Iran has been working on since 1989, which would be required to develop the essentials for a clandestine nuclear weapon. It tries to establish a narrative whereby it documents that it has been extremely prudent and careful in looking at all the evidence. [The IAEA] has tried to multisource as much of the information as possible, and it points out repeatedly that the report is not only based on information that the agency got itself, but that it also relied on about a dozen or more member states to corroborate the information that [it] obtained in Iran.

So if you're a country like Israel that feels threatened by Iran, does this confirm your fears or does it show that Iran still has a way to go?

It certainly confirms your fears that Iran is working on research and development of nuclear weapons in a very systematic way. One of the things that the report does is that it lays out, on page five of the annex, a chart showing the organization of the nuclear program in Iran, which shows that the military and the civilian nuclear programs are interconnected. That's something that people are very worried about because the military program has been, to a large extent, hidden in Iran. We've been told by the Iranians that the nuclear program is a civilian one, but the IAEA documents that there is a complex interaction between the military and the civilian organizations that are responsible for nuclear power development.

In 2007, the CIA issued a public report (NYT) that said Iran had stopped working on a nuclear weapon in 2003. Does this report contradict that?

What this report says is that through about 2003, the IAEA was confident that it had a very good understanding of nuclear weapons development by Iran. [But] after 2003, there are gaps in their knowledge because Iran was no longer cooperating with the agency. It also doesn't answer the question "yes or no," as to whether Iran has a nuclear weapons program. And it doesn't answer the question "yes or no," as to whether it did have one as opposed to not having one now. But when you look at the entire gamut of activities that are described in that technical annex, which I think is about twelve pages, the impression you have is that all of these things together look like a nuclear weapons program. That's of great concern.

Do you think the United States is coming to a different conclusion than it did a few years ago?

The report does suggest that in a couple of critical areas beyond 2003, Iran has continued to do work on some of the items that it lists as being critical or useful for nuclear weapon programs. So the IAEA does in fact state that some of this activity has continued until the present. It asks to questions: Is it all continuing? Are they just doing a little bit of it? In the U.S. government, there are people hammering away on the idea that Iran has continued nuclear weapons work, that the work has perhaps gone further underground than had been believed before, but that the work has continued. You do have a few people in the U.S. government who have said, "Wait a minute. Our last assessment was that the activity is not continuing, that it was interrupted perhaps in 2003 or 2004, and that we don't have any indication that the work has continued." So when you finish the report, the bottom line is some of the activity has been going on, but there are statements in the report suggesting that critical areas were interrupted by the Iranian government a few years ago because they were worried about being caught.

Was that because the United States invaded Iraq in 2003?

Many people in Western governments who have been weighing in on this question [believe] that when the United States appeared to be successful in Iraq, the Iranians were concerned that the United States [would] turn its guns on Iran and try to make regime change in Iran. That might have persuaded Iran to cease its nuclear program. They were concerned about detection. One of the things that the IAEA documents--and spells out in a way [unlike] in previous reports--is that all three uranium enrichment plants that Iran has declared to the agency (Natanz, Tehran, and Fordow) and is now operating under safeguards were clandestine facilities. That is a significant development because it underscores that Iran has a history of two decades or more of deception and failure to disclose. I've heard again and again from people in Western governments that some of these activities were carried out by Japan, Sweden, Switzerland, and by Germany. But the difference is that these countries do not have a legacy of deception and noncooperation with the international community and the IAEA.

The Iranians do not have any credibility in making assertions that the reports about these activities are falsifications. The IAEA knows that it has to be careful. In the run-up to the second Gulf War, the IAEA and the Bush administration went to the mat over this. The agency's credibility was on the line. So since 2002, the agency has to be extremely careful that it doesn't get misled by member states, particularly important ones like the United States, with a huge number of assets in the intelligence area.

So for people who aren't experts, what's the bottom line? Is Iran close to a nuclear weapon?

The information presented in this report shows that there is a very full range of activities that the Iranians are carrying out on all fronts that would be useful for a nuclear weapon. The question that remains in my mind is whether these activities are carried out by organizations on their own, or whether it's directed from the top. The IAEA report seems to imply that there is, in fact, an organizational structure that is giving orders to people to do these things. That's very worrying, because if it were to be confirmed that directions are being given at the top of the Iranian government to carry out these activities, that would suggest a [high-level] decision to do a program that looks like a nuclear weapons development program. The explanation given by the Iranians in a number of these cases in 2007 and 2008 was that they were individual programs that were unconnected, where individual scientists and R&D organizations were carrying out activities that could have a civilian use. What the IAEA report shows is that there is a deep structure that links the military and the civilian program, and that somewhere in the background there may be people at the top of the Iranian government who are giving orders.

You have written recently about a meeting in 2004 between then-IAEA director Mohamed ElBaradei and former Iranian president Akbar Hashemi Rafsanjani. Is that relevant to this discussion?

Rafsanjani, during the meeting, actually became very emotional and almost broke into tears. He was explaining to people at the meeting with the IAEA that he had been on the front of the Iran-Iraq War during the 1980s and had seen the Iranian soldiers who had been attacked with chemicals by Iraq. People at the IAEA who have been looking at the Iranian program have thought about that meeting again and again. The Iranians were at war with Iraq; Iraq had unleashed chemical weapons on them. Many people who have been studying this program in Iran since then have wondered whether the Iranian leadership, after the Iran-Iraq War, took a decision to develop a nuclear weapons capability in secret to make sure that the kind of vulnerability Iran experienced in the Iraq War would never happen again. The IAEA's report doesn't answer that question.

How long do you think it would take for the Iranians to actually have nuclear weapons?

I can't really say. What the IAEA does in this report is delineates and describes R&D activities to develop capabilities that would be useful for a nuclear program.

In other words, the report says that the Iranians seem to be working on the possibility of making nuclear weapons, but we don't know if they will actually make them, or how long it will take them.

Right, and a good example is the discussion about nuclear testing. It talks about preparatory activities that indicate Iran organized and prepared to have a nuclear weapons test. What it doesn't do is provide us any insight as to whether or not they're building testing shafts, whether they're setting up an infrastructure to actually test a nuclear weapon--the kinds of things that happened in the Manhattan Project [the U.S. program to build the atomic bomb during World War II] that went on for several years. It doesn't go that far. It talks about pieces of information that [indicate] there were preparations carried out by Iran about how to organize a nuclear weapons test, but it doesn't cross the line and say, "Gotcha! We know that you're planning to test a nuclear weapon and this is your timeline."