Iranian officials claim they are pursuing nuclear technology for peaceful civilian purposes only, such as generating electricity. But most international proliferation experts suspect the fundamentalist Muslim theocracy is using its nuclear program to enrich uranium to higher levels than necessary for civilian nuclear-energy production and secretly trying to manufacture nuclear weapons.

Since the revelations of Tehran’s nuclear ambitions became public in 2002, the United Statesand other countries have been pressuring Iran to halt the program. TheUnited Statesrefused to deal directly with Tehran, but the European Union began negotiations to reach a diplomatic solution to the standoff. In late 2004, U.S. officials agreed to support European efforts. In November of that year, Iran negotiated a deal with Britain, France, and Germany: The Europeans promised to give Iran economic incentives and assistance with its civilian nuclear program, and Iran promised to halt uranium enrichment.

After Iranian dissidents blew the whistle in 2002, Tehran admitted withholding information for nearly twenty years from the International Atomic Energy Agency (IAEA), the United Nations’ (UN) nuclear watchdog, about aspects of a uranium-enrichment program. Mahmoud Ahmedinejad, Iran’s new president, said after he was elected in June that Iran had a right to a nuclear program. In August, Iran also resumed sensitive nuclear work at some of its facilities, bringing two years of negotiations with the European Union on its nuclear program nearly to collapse.

Under the terms of the Nuclear Non-Proliferation Treaty (NPT), which governs nuclear-energy use around the world, any nation can enrich uranium for civilian nuclear-power reactors. Uranium enrichment is a critical part of both nuclear energy and nuclear-weapons programs. During the enrichment process, naturally occurring uranium is converted into nuclear fuel. Depending on its enrichment level, this fuel can power either energy plants or, in a more refined state, nuclear weapons. Under Article IV of the NPT, which Iran ratified in 1968, a country can develop its nuclear-power capacity under a legal civilian program. Then the country could give ninety days’ notice that it intends to drop out of the NPT, convert its civilian nuclear program to a nuclear-weapons program, and declare itself a nuclear-armed power.

Its program has facilities considered legal under international agreements—that is, declared to the world and open to IAEA inspections—and facilities that were either kept secret or are suspected of hosting activities not permitted by international agreements.

The legal facilities include:

• A light-water commercial nuclear reactor at Bushehr, a city on the Persian Gulf coast of southwestern Iran. Iranian officials say the facility, which will be Iran’s first operational reactor when it opens in 2006, will use nuclear energy to generate electricity only. Russia helped build the $800 million reactor and signed a deal with Iran March 1 that guarantees a supply of Russian fuel for Bushehr. Russia also agreed to remove all of Bushehr’s spent fuel to prevent its use in an illicit nuclear-weapons program. The United States opposed the deal. Experts say Bushehr will produce enough spent fuel—which can potentially be reprocessed to produce plutonium suitable for fueling nuclear weapons—for about thirty atomic bombs per year.  
• Several small research reactors, which are not considered proliferation risks because they produce only very small amounts—grams, not kilograms—of nuclear material.

The facilities that were previously undisclosed or host suspect activities include:

• Isfahan. The uranium-conversion facility at Isfahan in central Iran is capable of converting yellowcake into uranium hexafluoride (UF-6), a gas used in centrifuges to produce weapons-grade uranium. In May, Iran revealed for the first time that it had used the Isfahan facility to convert thirty-seven tons of yellowcake into the gas uranium tetrafluoride (UF-4), a precursor to UF-6.
• Natanz. Many experts suspect the UF-6 produced at Isfahan is taken to an enrichment facility at Natanz in central Iran, which was secret until Iranian dissidents revealed its existence in August 2002. There the gas is enriched—by being spun in high-speed centrifuges—to the relatively low level required to fuel electricity-generating power plants or to the higher level needed for nuclear bombs.

  There are at least two plants at Natanz, says Charles Ferguson, a nuclear expert and the science and technology fellow at the Council on Foreign Relations. One is a small-scale pilot plant that was likely used to test centrifuges and enrich small amounts of uranium; the other facility is a bigger, commercial-scale plant able to enrich much larger amounts of uranium. According to information from IAEA investigations, Iran has completed neither the pilot-scale nor the commercial-scale enrichment plants, although the pilot-scale plant houses more than 100 centrifuges. A commercial-scale plant would have as many as 50,000 of that type of centrifuge, Ferguson says. After the 2002 revelations, Iran admitted the existence of the Natanz facilities and allowed IAEA chief Mohammed ElBaradei to tour them in February 2003. In August 2003, IAEA inspectors found samples of highly enriched uranium, which Iran is not allowed to have under the NPT, on some of the centrifuges at Natanz. Tehran claimed the centrifuges—which were likely purchased from the network of rogue Pakistani nuclear scientist A.Q. Khan—were already contaminated with the material when Iran received them. An independent panel of experts confirmed this claim in August; nonetheless, a U.S. State Department spokesman said August 23 that the report didn’t prove Iran ’s innocence, saying there are still “unresolved concerns” and “open questions” about the country’s nuclear intentions.

• Arak. Experts say the planned heavy-water research reactor is about five years from completion. Once the plant is operational, it could produce enough plutonium for about one nuclear bomb per year.

Iran has long pursued nuclear energy and weapons, experts say. “The shah had these aspirations,” says Ashton Carter, a former assistant secretary of defense for international security policy and the Ford Foundation professor of science and international affairs at Harvard University. Shah Mohammed Reza Pahlavi governed Iran from 1941 to 1979, except for a brief period in 1953. In the 1970s, Iran had a fledgling program to develop nuclear weapons even as it negotiated to buy nuclear reactors from France, Germany, and the United States, experts say.

Yes, experts say, and it is widespread and enthusiastic. Many Iranians feel, and their leaders reiterate, that as a great state, Iran should have access to nuclear technology, experts say. Iranian officials have repeatedly defended their right to a nuclear-energy program, also citing possible threats from Israel and U.S. forces in the region.

It’s unlikely at the moment. The U.S. military is already stretched thin in Iraq, Afghanistan, and elsewhere, and there would be little domestic support for another war, many experts say. But Bush said August 13 that “all options are on the table” regarding Iran. “If you tried and failed in negotiations—really tried and failed—force is something to consider,” says Robert Gallucci, a former ambassador-at-large for nonproliferation issues and dean of the Georgetown University School of Foreign Service. One possibility is that the United States or Israel could carry out a disabling pre-emptive strike on Iran’s nuclear facilities. However, Iranian officials have issued strongly worded warnings against such an attack, saying they would retaliate.