Here are the main developments in Iran’s nuclear programme since 2015, when Tehran, which the West suspected of trying to build an atomic bomb, agreed to limit its uranium enrichment activities.
In 2013, newly elected Iranian president Hassan Rouhani says he is ready for “serious” negotiations on Iran’s nuclear programme, following an eight-year stalemate under ultraconservative Mahmoud Ahmadinejad.
Rouhani secures support from supreme leader Ayatollah Ali Khamenei for efforts to break the deadlock.
On July 14, 2015, Iran and the five permanent members of the UN Security Council – Britain, China, France, Russia and the US – plus Germany reach a historic accord in Vienna.
The deal places significant restrictions on Iran’s nuclear programme in exchange for sanctions relief after 12 years of crisis and 21 months of protracted negotiations. It comes into force on January 16, 2016.
Under the accord, Tehran’s nuclear programme is placed under strict UN control subject to guarantees it is not trying to make an atom bomb, something Iran has always denied.
Trump pulls out
US president Donald Trump walks away from the deal on May 8, 2018.
“We cannot prevent an Iranian nuclear bomb under the decaying and rotten structure of the current agreement,” he says.
Deal critics had complained from the start about the time limits applied to the deal.
Later in 2018, Washington begins reimposing sanctions on Iran and companies with ties to it, hitting the central bank and the country’s vital oil sector.
Major international firms halt activities in the country.
Iran walks back
In May 2019, Iran starts rolling back on its deal commitments in retaliation.
Trump hits back by sanctioning Iran’s steel and mining sectors.
Tehran increases its stockpile of enriched uranium in excess of the limits laid down in the deal.
It announces in early 2020 it is foregoing a limit on its number of uranium-enriching centrifuges.
In 2021, Iran says it has started enriching uranium to up to 60 percent – many times the limit of 3.67 percent imposed by the deal – which the International Atomic Energy Agency (IAEA) says could be sufficient to create a compact nuclear explosive.
In April 2021, with President Joe Biden now in the White House, talks on rescuing the accord start in Vienna.
Iran’s new ultraconservative president, Ebrahim Raisi, says in August he is open to negotiations but will not be pressured by sanctions.
Talks resume in November.
Just as a deal looks imminent, Russia invades Ukraine on February 24, 2022 and Moscow becomes the target of international sanctions.
The Iran nuclear negotiations are halted as Russia seeks guarantees from Washington that the measures targeting its economy will not affect its cooperation with Iran.
In mid-March, Washington says a compromise is “close”, but Tehran raises some “red line” issues, including its bid to have all sanctions lifted.
New US sanctions
On March 30, Washington sanctions suppliers to Tehran’s ballistic missiles programme, which Iran dubs “another sign of the US government’s malice” towards the Islamic republic.
On May 13, the EU announces progress in talks to revive the nuclear deal but days later US chief negotiator Rob Malley says the chances of success are slimmer than that of failure.
Nuclear watchdog raps Iran
On June 8, the IAEA adopts a resolution submitted by the Britain, France, Germany and the US that condemns Iran for the first time in two years.
The resolution, which China and Russia reject and which Tehran slams as “political”, comes after the IAEA raises concerns about traces of enriched uranium found at three sites Iran had not declared as having nuclear activities.