Here is a look at recent events involving Iran's nuclear programme nearly a decade since the dispute erupted after Iranian exiles blew the whistle on a secret uranium enrichment plant at Natanz and a heavy water plant at Arak.
Oct. 1, 2009 - Iran meets six world powers in Geneva and approves in principle a plan to send 75 percent of its low-enriched uranium to Russia and France, where it would be made into special fuel for a Tehran reactor making medical materials.
Oct. 25 - U.N. nuclear experts inspect a newly disclosed enrichment plant being built inside a mountain bunker.
Oct. 30 - Iran tells the International Atomic Energy Agency (IAEA) it wants fresh nuclear fuel for a reactor in Tehran before it will agree to ship enriched uranium stocks to Russia and France, according to U.N. officials.
Nov. 18 - Tehran says it won't send enriched uranium abroad but will consider swapping it for nuclear fuel on Iranian soil.
Nov. 27 - The IAEA's 35-nation governing board censures Iran for developing the Fordow plant near Qom in secret and demands Iran freeze the project. Iran rejects the demand.
Jan. 19, 2010 - Iran rejects major parts of the deal to send abroad for processing most of its enrichment material.
Feb. 9 - Iran begins making higher-grade nuclear fuel, enriched to a level of 20 percent, at the Natanz plant.
Feb. 18 - An IAEA report suggests for the first time Iran might be actively chasing a nuclear weapons capability rather than merely having done so in the past.
May 17 - Iran, Brazil and Turkey sign a nuclear fuel swap deal. Iran says it has agreed to transfer low-enriched uranium to Turkey within a month in return for higher-enriched nuclear fuel for a medical research reactor. The deal is not implemented due to a lack of U.S., French and Russian involvement.
June 9 - U.N. Security Council votes to expand sanctions against Iran to undermine its banking and other industries. U.S. Congress approves new unilateral sanctions on June 24.
Dec. 5 - Nuclear energy chief Ali Akbar Salehi says Iran will use domestically produced uranium concentrates, known as yellowcake, for the first time at a nuclear facility, cutting reliance on imports of the ingredient for nuclear fuel.
Dec. 6 - Talks begin in Geneva between Iranian nuclear negotiator Saeed Jalili and EU foreign policy chief Catherine Ashton, who is leading the discussions on behalf of big powers.
Jan. 21, 2011 - World powers fail to prise any concessions from Iran in the talks, calling the discussions disappointing and saying no further meetings are planned.
June 9 - Russia and China join Western powers in telling Iran its "consistent failure" to comply with U.N. resolutions "deepened concerns" about possible military dimensions to its nuclear programme.
Sept. 3 - Russian-built Bushehr nuclear power plant begins to provide electricity to the national grid, state news agency IRNA reports.
Feb. 15, 2012 - Iran proclaims nuclear advances, including new centrifuges able to enrich uranium much faster. The next day Iran proposes a resumption of nuclear talks with world powers.
Feb. 20-21 - Senior U.N. inspectors end a second round of talks in Tehran without success and without Iran relenting on a refusal to let IAEA inspect a military site at Parchin.
March 5 - Iran has tripled its monthly production of higher-grade enriched uranium and the IAEA has "serious concerns" about possible military dimensions to Tehran's activities, IAEA head Yukiya Amano says.
March 6 - EU foreign policy chief Catherine Ashton accepts Iran's offer of new talks after a year's standstill. On the same day Iran says it will let U.N. nuclear inspectors visit Parchin but diplomats note a proviso saying access to the site hinges on a broader agreement on outstanding issues.
April 14 - Talks between Iran and the United States, France, Germany, China, Russia and Britain resume in Istanbul. Discussions are inconclusive but good enough to schedule another round in May.
May 4 - Iran says it will never suspend its uranium enrichment programme and sees no reason to close the Fordow underground site, making clear Tehran's red lines in nuclear talks with world powers later this month.
May 21 - IAEA chief Yukiya Amano goes to Iran for impromptu talks with the head of Iran's nuclear energy organisation, Fereydoun Abbasi-Davani. He is later to meet chief nuclear negotiator, Saeed Jalili and Foreign Minister Ali Akbar Salehi just two days before the six-power round with Iran in Baghdad.