April 16, 2006 -- Here are some of the decisive moments in Iran's pursuit of nuclear weapons.
1968: Iran signs the Non-Proliferation Treaty (NPT) in July 1968, ratifies it in February of 1970, and concludes a full-scope Safeguards Agreement with the International Atomic Energy Agency (IAEA) in June 1973.
1974: The German firm Siemens begins work on two reactors at Bushehr. When work stops following the 1979 revolution, one Unit 1 is near completion with more than half of its equipment installed; the second unit is 50 percent complete.
1985-1987: Iran begins a centrifuge enrichment program based on open source literature. In 1987 it acquires drawings for a P-1 centrifuge through the A.Q. Khan network (referred to in IAEA report as "clandestine supply network.")
1991: Iran secretly imports from China approximately one metric ton of uranium hexafluoride (UF6). Neither country reports the transfer to the IAEA.
1995: Work resumes at the two reactors in Bushehr, under a contract with Russia in 1995.
1999: Iran tests centrifuges.
2001: Construction begins at Natanz on two facilities -- a small scale enrichment plant that is designed to hold 1,000 centrifuges and a larger one that will eventually house 50,000 P-1 centrifuges.
August 14, 2002: Iran's Nuclear Program Outed: National Council Of Resistance Of Iran holds press conference in Washington D.C. to reveal the existence of nuclear activity at Natanz and Arak, as well as work in other areas of weapons of mass destruction (WMD.)
October 2003: Iran admits to the IAEA that it conducted "a limited number of tests using small amounts of UF6" in 1999 and 2002 at Kalaye Electric Company.
Nov. 10, 2003: Iran suspends uranium enrichment and announces it will allow tougher UN inspections of its nuclear facilities by accepting the Additional Protocol (Enhanced Safeguards). The Protocol allows, among other things, the unannounced inspection of suspect facilities. Iran signs the Additional Protocol on Dec. 18, 2003.
Nov. 15, 2004: Suspension Agreement: Iran agrees to a voluntary suspension of uranium enrichment and related activities while further talks are held. The agreement applies to all enrichment related and reprocessing activities, including "the manufacture and import of gas centrifuges and their components; and the assembly, installation, testing or operation of gas centrifuges."
August 2005: Mahmoud Ahmadinejad is installed as Iranian president; Iran promises "irreversible" resumption of enrichment. On August 15, Iran removes IAEA seals from uranium hexafluoride conversion lines at Esfahan.
September 24, 2005: IAEA Resolution finds Iran in noncompliance with its NPT obligations but defers referral to UN Security Council to give EU-3-led diplomacy an opportunity to work.
January-February 2006: Iran breaks IAEA seals at Natanz and resumes uranium enrichment.
March 29, 2006: Security Council issues Presidential Statement calling on Iran to suspend enrichment and related activity and adhere to the Additional Protocol. The IAEA is asked to report on Iran's compliance in 30 days.
April 11, 2006: Iran announces tha it has produced a small quantity of reactor grade (3.5 percent enriched) uranium using its centrifuges at Natanz.