We are having some success in clarifying what the NIE (U.S. National Intelligence Estimate on Iran) actually means. What it does mean is that we have information that at some time back in 2003, Iran stopped its activity in the area of designing a warhead. That’s what they stopped doing. But building a nuclear weapon involves three distinct activities. One is to acquire the fissile material, and as you know that activity continues in Iran. They are continuing their work on enriching uranium. Another is to develop a delivery system. And of course the Iranians are working hard on he acquisition and development of missile technology, and they are already have a lot of missiles. And thirdly, of course, the actual warhead. So its only the work on the warhead that stopped, and we don’t even have absolute certainty that activity has not resumed.
Council on Foreign Relations, February 4, 2008