Timeline: Iranian nuclear dispute

Here is a look at events involving Iran's nuclear program:

October 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.

October 25 - U.N. nuclear experts inspect a newly disclosed enrichment plant being built inside a mountain bunker at Fordow.

October 30 - Iran tells the International Atomic Energy Agency (IAEA) it wants fresh nuclear fuel for its Tehran medical research reactor before it will agree to ship enriched uranium stocks to Russia and France, according to U.N. officials.

November 18 - Tehran says it won't send enriched uranium abroad but will consider swapping it for nuclear fuel on Iranian soil.

November 27 - The IAEA's 35-nation governing board censures Iran for developing the Fordow plant in secret and demands Iran freeze the project. Iran rejects the demand.

- - - -

January 19, 2010 - Iran rejects major parts of the deal to send most of its enrichment material abroad for processing.

February 9 - Iran begins making higher-grade nuclear fuel, enriched to a level of 20 percent, at its Natanz plant.

February 18 - An IAEA report suggests for the first time Iran might be actively chasing nuclear weapons capability.

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. U.S. Congress approves new unilateral sanctions on June 24.

December 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.

December 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.

- - - -

January 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 program.

September 3 - Iran says its Russian-built Bushehr nuclear power plant begins to provide electricity to the national grid.

- - - -

February 15, 2012 - Iran proclaims nuclear advances, including new centrifuges able to enrich uranium much faster. The next day it proposes a resumption of nuclear talks with world powers.

February 20-21 - Senior U.N. inspectors end a second round of talks in Tehran without success and with Iran continuing to refuse to let IAEA inspect a suspect 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 21 - IAEA chief, Yukiya Amano, makes a short-notice trip to Iran and says talks with nuclear negotiator Jalili are extensive and would have a positive impact on negotiations.

May 25 - Iran and world powers talk again in Baghdad and agree to hold another session the following month.

June 8 - The IAEA says it made no progress in its talks with Iran about suspected nuclear weapons research and calls the outcome "disappointing".

June 11 - Chief nuclear negotiator Saeed Jalili agrees to focus on the six powers' demands at Moscow talks on June 18 and discuss a proposal to curb production of high-grade uranium.

June 18 - Talks begin in Moscow.

(Reporting by David Cutler, London Editorial Reference Unit)