Iran nuclear crisis timeline

Tehran - Key developments in the standoff over Iran's nuclear programme:

2005

• Aug 8: Iran resumes uranium conversion activities which had been suspended since November 2004.

2006

• April 11: Iran says it has enriched its first uranium to 3.5% purity and later, in May, to 4.8%. This is insufficient to make a nuclear bomb.

• Dec 23: The UN Security Council imposes sanctions on Iran's trade in sensitive nuclear materials and technology. It strengthens the measures in 2007 and 2008.

2007

• April 9: President Mahmoud Ahmadinejad says Iran can produce nuclear fuel on an industrial scale.

2009

• April 9: Iran inaugurates its first nuclear fuel plant, and says it has installed 7 000 uranium enrichment centrifuges at Natanz.

• Sept 25-28: Iran reveals a secret uranium enrichment plant, Fordo, which is being built inside a mountain near the holy city of Qom.

2010

• June-July: World powers enact new military and financial sanctions.

• July 30: Iran says it is ready for immediate talks with the United States, Russia and France over an exchange of nuclear fuel.

• Aug 16: Iran announces it is to start building its third uranium enrichment plant in early 2011.

• Aug 21: Iran starts loading fuel into its Russian-built first nuclear plant at Bushehr.

• Nov 29: Twin blasts in Iran's capital kill a top nuclear scientist and injure another. Ahmadinejad blames Israel and the West.

2011

• Jan 22: Failure of new talks between Tehran and six world powers in Istanbul.

• May 23-24: The EU and US announce new sanctions against Iran.

• July 19: Iran says it has begun installing new centrifuges with better quality and speed.

• Aug 22: Iran says it has begun transferring centrifuges from Natanz to the Fordo underground site.

• Sept 2: The IAEA says it is getting worried about a possible military dimension to Iran's nuclear activities. It says since February 2007, Iran has produced more than 4 500 kilos of 3.5% enriched uranium at its Natanz site.

• Nov 8: An IAEA report points to "serious concerns" about Iran's nuclear activities, and "credible" information Tehran may have worked on developing atomic weapons.

• Dec 27: Iran says that no oil will pass through the key oil transit Strait of Hormuz if the West applies sanctions on its oil exports. The US warns Tehran it will not tolerate any attempt to disrupt shipping there.

2012

• Jan 1: Iran tests a new medium-range surface-to-air missile during war games near to the Strait of Hormuz after the United States unleashes extra sanctions that sends its currency to a record low.

• Jan 2: Iran test-fires a Qader ground-to-ship cruise missile, a short-range Nasr anti-ship missile and a Nour surface-to-surface missile near the strait.