Officials have told The Associated Press that Iran has revealed the existence of a second uranium enrichment plant.
The officials say Iran's announcement was in a letter sent Monday to International Atomic Energy Agency chief Mohamed ElBaradei.
Iran is under three sets of U.N. Security Council sanctions for refusing to freeze enrichment, which can make both nuclear fuel and warhead material. It had previously acknowledged having only one such facility.
The government officials - one speaking from his European capital outside Vienna, the other a diplomat in Vienna - demanded anonymity Friday because their information was confidential.