VIENNA, June 20, 2025 (BSS/AFP) - A week ago, Israel launched an 
unprecedented attack against Iran, saying the country was on the verge of 
developing a nuclear weapon, a claim Tehran has always denied.

Western powers have repeatedly expressed concerns about the rapid expansion 
of Iran's nuclear programme, questioning in particular the country's 
accelerated uranium enrichment.

The following is a recap of the main developments regarding Iran's nuclear 
programme, as European foreign ministers are holding nuclear talks with their 
Iranian counterpart in Switzerland on Friday.

- 'Structured programme' -

Iran laid the foundation for its nuclear programme in the late 1950s with 
technical assistance from the United States, when Iran's ruling shah, 
Mohammad Reza Pahlavi, signed a civilian nuclear cooperation agreement with 
the US.

In 1970, Iran ratified the Treaty on the Non-Proliferation of Nuclear Weapons 
(NPT), committing it to declare its nuclear material to the International 
Atomic Energy Agency (IAEA).

But revelations in the early 2000s about undeclared nuclear sites raised 
concerns. An 2011 IAEA report, collating "broadly credible" intelligence, 
said that at least until 2003 Iran "carried out activities relevant to the 
development of a nuclear explosive device".

- Historic accord left in tatters -

After suspending enrichment activities, Iran began talks with European and 
then international powers that would later culminate in a historic deal.

On July 14, 2015, Iran and the five permanent members of the UN Security 
Council -- Britain, China, France, Russia and the United States -- plus 
Germany reached an accord in Vienna.

The deal, called the Joint Comprehensive Plan of Action (JCPOA), placed 
significant restrictions on Iran's nuclear programme in exchange for 
sanctions relief after 12 years of crisis and 21 months of protracted 
negotiations.

But the hard-won deal began to unravel when the US under President Donald 
Trump walked away from it on May 8, 2018, and reimposed sanctions on Iran.

- 'Nuclear escalation' -

Following the US withdrawal, Iran retaliated by stepping up its nuclear 
activities as if "a red cape had been waved in front of a bull," said Clement 
Therme, associate researcher at the Rasanah International Institute for 
Iranian Studies.

According to Therme, Iran "embarked on a strategy of escalation" in a bid to 
up pressure and obtain help to circumvent sanctions. But Tehran's moves were 
unsuccessful and came at an "exorbitant economic cost".

Iran first began enriching uranium to five percent -- breaching the limit of 
3.67 percent imposed by the deal -- before it raised the enrichment levels to 
20 and then to 60 percent in 2021, which is a short step from the 90 percent 
required for use in a weapon.

Iran has also increased its stockpiles of enriched uranium, which was set at 
202.8 kilogrammes under the deal. Iran's total enriched uranium stockpile is 
currently believed to be more than 45 times that limit.

And Tehran has since exceeded the number of centrifuges -- the machines used 
to enrich uranium -- it is allowed to have while beginning to produce more 
material faster by using advanced models at its plants.

Efforts to revive the deal have been fruitless so far, with European-led 
talks on hold since summer 2022.

After Trump's return to the White House, talks between Washington and Iran 
and mediated by Oman resumed in April.

While the US president has voiced confidence that Iran would eventually sign 
a nuclear deal, Tehran has said that Israeli strikes that targeted a slew of 
military and nuclear sites "dealt a blow" to diplomacy.

- 'No indication' -

Faced with Iran's rapidly expanding nuclear programme, the IAEA expressed 
"serious concern" in its latest quarterly report at the end of May.

According to the UN agency, Iran is the only non-nuclear weapon state to 
enrich uranium to 60 percent. It theoretically has enough near-weapons-grade 
material, if further refined, for more than nine bombs.

However, the manufacturing and delivering of a nuclear bomb requires many 
other steps, including mastering both ballistics and the miniaturisation of 
the nuclear charge.

The IAEA has said it currently has "no indication" of the existence of a 
"systematic programme" in Iran to produce a nuclear weapon.

US Director of National Intelligence Tulsi Gabbard testified to a Senate 
committee in March that Iran was not actively building a nuclear bomb.

Iran has always denied having such ambitions, regularly referring to a long-
standing fatwa, or religious edict, by Iran's supreme leader Ayatollah Ali 
Khamenei prohibiting atomic weapons.