Since Friday, June 13, Iran has been the target of intense Israeli airstrikes. Israeli Prime Minister Benjamin Netanyahu and his government have justified the attack by the need to "eliminate" the "threat" posed by Iran's military program, focusing its initial strikes on the regime's atomic infrastructure.
For years, Israel has warned that its enemy was on the verge of acquiring nuclear weapons, but events have accelerated recently. On Thursday, just hours before the strikes, Iran's clerical leadership announced a "significant" increase in enriched uranium production, as talks with the United States were at an impasse. Does this mean that Tehran was, this time, very close to acquiring a nuclear bomb?
The Islamic regime, which came to power in 1979, has always denied the pursuit of a nuclear weapons development program. Tehran insists its program is strictly "peaceful" and intended only for the development of civilian nuclear power plants. In November 2024, Esmaeil Baghaei, spokesperson for Iran's Foreign Ministry, reiterated that the "problems" raised by the program were a result of a "misunderstanding."
In the name of developing civilian nuclear power, Tehran says it has the right to enrich uranium and has made the ban on enrichment a red line for signing any new international deal. "No enrichment, no deal. No nuclear weapons, we have a deal," summarized Iranian Foreign Minister Abbas Araghchi on Wednesday, June 4.
Various sources, compiled by the International Atomic Energy Agency (IAEA) and Israeli intelligence, nonetheless confirmed that a program named "AMAD," aimed at developing nuclear weapons, existed in Iran in the early 2000s. It was reportedly dismantled in 2003. Afterward, Tehran created the Organization of Defensive Innovation and Research (SNPD, its Persian acronym), but has denied that this organization had a military purpose. According to Mossad, Israel's foreign intelligence service, both the AMAD program and the SNPD were led by Mohsen Fakhrizadeh, an Iranian physicist who was assassinated in 2020 in an attack attributed to Israel.
The development of nuclear power also acts as a unifying issue for the Iranian population. According to Amélie Chelly, an Iran specialist and researcher at Sorbonne-Nouvelle University, the vast majority of Iranians oppose the current regime but support nuclear efforts to "sanctuarize the territory."
To distinguish between the development of a civilian nuclear program and the pursuit of a nuclear weapon, observers focus on the percentage of uranium enrichment, one of the key materials needed for a nuclear chain reaction. While civilian nuclear power (used by Iran in its only nuclear plant, located at Bushehr) requires enrichment of just 3% to 5%, several elements suggest Tehran is seeking to go much further.
Uranium is a heavy metal and a naturally radioactive element. It is abundant on Earth and can be found in small quantities in rock, soil, or water. The three main forms of uranium atoms, known as isotopes, are uranium-234, uranium-235, and uranium-238.
Uranium-235 is the only naturally fissile isotope, meaning it can sustain a nuclear fission reaction. However, it is extremely rare. Extracted uranium is composed of more than 99% uranium-238 by mass and just 0.7% uranium-235. To be used as fuel in a nuclear power plant or in the manufacture of a bomb, natural uranium must therefore be "enriched" with uranium-235 – that is, the isotopic concentration of uranium-235 must be increased.
"Low-enriched" uranium contains less than 20% uranium-235. Most commercial civilian reactors use fuel enriched between 3% and 5% to produce electricity.
"Highly enriched" uranium has a concentration above 20%. It is mainly used in naval propulsion reactors, such as submarines, or in certain research reactors.
To manufacture a nuclear weapon, uranium must be enriched to 90%. This is a lengthy and laborious process that requires several thousand centrifuges. Iran already possesses a large number – around 14,000, according to figures from the International Atomic Energy Agency (IAEA) cited on Friday, June 13, by the New York Times – across several sites, such as at Natanz, south of Tehran.
According to the IAEA, the only international body authorized to inspect facilities on site, Tehran is now capable of producing 34 kilograms of uranium enriched to 60% per month. In its March 2025 report, the agency estimated, based on data provided by the Islamic Republic, that the country then had 274.8 kilograms of uranium enriched to 60%.
This graph shows the stocks of enriched uranium found by the IAEA in Iran, generally minimum estimates.
While uranium enriched to 60% is not usable, Iran's nuclear program is approaching the 90% threshold required to produce nuclear weapons. With its current stockpile, Iran could be capable of producing "more than nine" bombs, the European troika (France, Germany and the United Kingdom) told the IAEA Board of Governors on Thursday, June 12. According to European diplomats, there is no doubt that "Iran has continued its nuclear escalation unabatedly, even further beyond any credible civilian justification."
That being said, it remains very difficult to know how much time Tehran would still need to acquire the bomb. According to Jeffrey Lewis, director of the East Asia Nonproliferation Program at the Middlebury Institute of International Studies at Monterey, California, who spoke to Le Monde, the estimated timeline, prior to the Israeli attack, was "a year or a few months." However, he added some nuance: "Iran has been a few months away from the nuclear bomb for 15 years."
Objectively assessing Tehran's potential to acquire the bomb is all the more complex because the regime deliberately maintains a degree of opacity. In its June 2025 report, the IAEA denounced maneuvers aimed at preventing it from conducting its "verification activities" on site, or the inability to "provide (…) technically credible explanations for the presence of uranium particles (…) at several undeclared locations." The agency mentioned a series of "concealment efforts," notably "extensive sanitization" and the "provision of inaccurate explanations" by authorities, preventing the IAEA from having "assurance that Iran's nuclear programme is exclusively peaceful."
Iran began a civilian nuclear program in the 1950s, under the shah's regime. In 1968, the Iranian leader, an ally of Western powers, signed the Treaty on the Non-Proliferation of Nuclear Weapons, which aims to prohibit the use of atomic energy for military purposes. In doing so, Iran pledged never to produce nuclear weapons.
The revolution in 1979 and the rise to power of the Islamists effectively stopped the nuclear program. It was then discreetly restarted, with Tehran gradually acquiring the necessary facilities to produce enriched uranium. In January 2006, President Mahmoud Ahmadinejad announced that "Iran has joined the group of those countries which have nuclear technology" – a bombshell statement, given that the country at that time only mastered enrichment to 3.5%. While there was no official mention of military ambitions, Iran's program worried the international community enough to justify the imposition of severe financial sanctions on the country.
In July 2015, after years of negotiations, Iran and the "P5+1 group" (US, Russia, China, France, UK and Germany) reached a deal, which committed to limiting its production to civilian purposes in exchange for the lifting of international sanctions. Nevertheless, doubts persisted about Iran's willingness to honor its commitments.
Trump, deeming the agreement negotiated by his predecessor Barack Obama (2009-2017) ineffective, decided to withdraw from the deal in May 2018. The US then reinstated sanctions against the Iranian regime, and Tehran decided to resume uranium enrichment as of November 2019, then at 4.5%.
After returning to the White House on January 20, 2025, Trump reestablished contact with Iran starting in April, hoping to negotiate a deal on the nuclear issue. The fifth round of talks ended in May without significant progress: Tehran refused to reverse its uranium enrichment, while Washington insisted that Iran's capabilities in this area be reduced to zero. The latest round of negotiations between American and Iranian officials, scheduled for Sunday, June 15, in Muscat, Oman, was canceled because of the Israeli attack.
Translation of an original article published in French on lemonde.fr; the publisher may only be liable for the French version.