Below is a timeline on Iran's nuclear program and Tehran's negotiations with Western powers over the last year:
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 (LEU) 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 near the Shi'ite holy city of Qom.
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 some enriched uranium stocks to Russia and France, according to UN officials.
Nov. 18 - Iran says Tehran will not send enriched uranium abroad for further processing but would consider swapping it for nuclear fuel within its borders.
Nov. 19 - U.S. President Obama warns Iran of the consequences of its failure to respond to the nuclear deal.
Nov. 26 - Outgoing U.N. nuclear watchdog chief ElBaradei says Iran's blockage of the proposal to divest it of possible nuclear bomb material is "disappointing".
Nov. 27 - The IAEA's 35-nation governing board censures Iran for developing the plant near Qom in secret and demands Iran freeze the project. Iran rejects the demand.
Nov. 29 - Iran says it plans to build 10 more enrichment sites.
Jan. 19, 2010 - Iran rejects key parts of the deal to send abroad for processing most of its enrichment material.
Feb. 2 - President Mahmoud Ahmadinejad says Iran is ready to send enriched uranium abroad, apparently easing his position.
Feb. 9 - Iran begins making higher-grade nuclear fuel, enriched to a higher level of 20 percent, at Natanz facility.
Feb. 18 - An IAEA report suggests, bluntly and for the first time that Iran is actively pursuing nuclear weapons capability.
April 19 - Iran says it will start work on a new uranium enrichment plant, in addition to the Natanz and Qom sites.
April 27 - Brazil offers to mediate to help end the West's diplomatic standoff with Iran over nuclear issues.
May 12 - UN resolutions aimed at increasing sanctions against Iran over its nuclear program "are not worth a penny" and Tehran will give no ground to pressure, Ahmadinejad says.
May 17 - Iran, Brazil and Turkey sign a nuclear fuel swap deal. Iran says it has agreed to transfer 1.2 tons (2,646 lb) of its low-enriched uranium to Turkey within a month in return for higher-enriched nuclear fuel for a medical research reactor.
May 31 - An IAEA report shows Iran's low-enriched uranium (LEU) stockpile is up to 2.4 tons. So, even if the proposed 1.2 tons were shipped out now it would still leave Iran enough material for a nuclear weapon if enriched to higher levels.
June 9 - The U.N. Security Council votes to expand sanctions against Iran to hit its banking and other industries.
June 24 - The U.S. Congress approves tough new unilateral sanctions aimed at squeezing Iran's energy and banking sectors, which could also hurt foreign companies doing business with Tehran. They are signed into law on July 1.
July 26 - The EU imposes tighter sanctions on Iran, aiming to block oil and gas investment and curtail its refining.
Iran says it is ready to hold talks on a nuclear fuel swap without conditions.
July 30 - Iran says it will never give up its right to refine uranium, but could suspend higher-level enrichment if a fuel swap can be agreed with foreign powers.
Aug. 6 - The Institute for Science and International Security (ISIS) says Iran is now using extra equipment to enrich uranium more efficiently at its Natanz pilot plant, stepping up its nuclear work despite sanctions.
Aug. 21 - Iran begins setting up fuel assemblies at Bushehr plant.
Aug. 30 - Iran announces it will produce in a year the nuclear fuel needed for the medical isotope reactor in Tehran.
Sept. 6 - An IAEA report says Iran has told inspectors that it had accumulated around 2.8 tons of LEU, about 370 kg (816 lb) more than in May.
Sept. 29 - Bushehr will begin supplying energy in early 2011, a senior official says, signaling a delay of several months after the spread of Stuxnet, a global computer virus believed to have affected mainly Iran.
Oct. 18 - Iran is ready to return to nuclear talks "as soon as tomorrow" but only if the subject of the negotiations is made clear in advance, says Abolfazl Zohrevan, deputy secretary of the Supreme National Security Council.
Oct. 26 - Iran says it has begun loading fuel into the core of the Bushehr nuclear plant.
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