On September 25, 2009, the United States, the United Kingdom, and France revealed that Iran had been building a clandestine uranium enrichment plant, and called for an immediate inspection of the site by the International Atomic Energy Agency (IAEA). Agency inspectors visited the plant one month later, and their preliminary findings were reported on November 16, 2009. According to the IAEA, the Fordow Fuel Enrichment Plant (FFEP), located about 20 km north of the city of Qum, is at an advanced stage of construction. Construction at the site began between 2002 and 2004 and resumed in 2006, in violation of U.N. Security Council resolutions requiring that Iran suspend all enrichment-related activities. Iran also failed to report its decision to build the enrichment plant, a requirement under Iran's inspection agreement with the Agency.

According to the United States, the Fordow plant is located in an underground tunnel complex on the grounds of an Islamic Revolutionary Guard Corps (IRGC) base. U.S. intelligence assessments indicate that uranium enrichment will not begin at the site until at least 2010; as of the IAEA's visit, no centrifuges had been installed. The facility is intended to hold approximately 3,000 centrifuges, which is inadequate to produce sufficient quantities of low-enriched uranium to fuel a nuclear power reactor. Iran claims that the plant will be used for centrifuge research and development; it could also be configured to produce enough highly enriched uranium for approximately one nuclear weapon per year, according to the United States.

Read reactions and analysis from around the world:

The Wisconsin Project argues that the enrichment plant near Qum could be part of a broader network of clandestine nuclear sites across Iran (see New York Times op-ed Lifting Iran's Nuclear Veil); The Wisconsin Project also outlines scenarios showing how Iran might use a secret enrichment plant to fuel a nuclear arsenal (see Qum's Nuclear Potential), 9-30-09.

U.S. officials condemn Iran's covert uranium enrichment plant and violations of U.N. Security Council resolutions, and call on Iran to fulfill its international obligations or face sanctions: Defense Secretary Robert Gates, Senator John Kerry, and State Department spokesperson, 9-09.

At a joint press conference with French President Nicolas Sarkozy and U.K. Prime Minister Gordon Brown, U.S. President Barak Obama says that "the size and configuration" of the Fordow plant is inconsistent with a peaceful nuclear program, 9-25-09.

Russian President Dmitry Medvedev expresses concern over the clandestine facility and encourages Iran to cooperate with the IAEA's inspection of the site, 9-25-09.

Canadian Prime Minister Stephen Harper appeals to Iran to cooperate with immediate IAEA inspections of the facility, 9-25-09.

Norwegian Foreign Minister Jonas Store states that there is a crisis of confidence between Iran and the international community and demands that Iran show full transparency regarding its nuclear facilities, 9-25-09.

U.N. Secretary-General Ban Ki-Moon conveys concern about continued Iranian activities related to uranium enrichment and summons Iran to implement U.N. Security Council resolutions and cooperate with the IAEA, 9-29-09.

The IAEA reports on its visit to Iran's newly disclosed enrichment plant, which the Agency says raises concern that Iran may have additional undeclared nuclear facilities, 11-16-09. (PDF)

Federation of American Scientists (FAS) calculates that Fordow is too small to be useful for enriching uranium for civilian nuclear reactors or for nuclear weapons in an article published by the Bulletin of Atomic Scientists, 11-23-09. FAS published an Issue Brief with calculations used to support their argument, 12-7-09. (PDF)

The Institute for Science and International Security (ISIS) concludes that Fordow could produce up to twice the weapons-grade uranium indicated by FAS, 11-30-09.