Iran's nuclear program poses a threat to many nations--particularly Israel and the United States. Yet, it is sometimes forgotten that Washington was an early supporter of Tehran's nuclear ambitions.

The United States provided peaceful nuclear assistance to Iran from 1957 to 1979, when the two states were allies. Washington exported the Tehran Research Reactor (TRR), enriched uranium to fuel it, and "hot cells," which can be used to produce plutonium--a critical ingredient for making nuclear weapons. All of this aid was provided for civilian uses, but it ended up indirectly augmenting Iran's nuclear weapons program. For example, from 1988 to 1992 Iran conducted covert plutonium reprocessing experiments using fuel pellets irradiated in the TRR.

The Iranian experience exposes a problem known as the dual-use dilemma: because nuclear technology has both peaceful and military applications, nuclear energy aid provides a potential foundation for a bomb program.

However, this danger has not deterred the United States from providing nuclear energy assistance to many countries. Today, for instance, Washington is in the midst of negotiating agreements with Jordan and Vietnam that would permit the sharing of nuclear technology, materials, and know-how.

Deals such as these could be a recipe for the further spread of nuclear weapons.

In a new book, I explore the relationship between peaceful nuclear assistance and nuclear proliferation. Based on an analysis of global nuclear commerce from 1945 to 2000, I show that states are much more likely to covet (and successfully build) nuclear weapons when they accumulate atomic assistance--particularly if they experience an international crisis after receiving aid.