Iran nuclear programme: What are ‘snapback’ sanctions that UN is reimposing?

United Nations sanctions on Iran over its nuclear programme are set to be reimposed on Sunday (September 28), after the Islamic Republic failed in its bid to stop the sanctions. This will put new pressure on Tehran as tensions in West Asia remain intense over Israel’s war with Hamas in Gaza.

The move has also raised the stakes in the stand-off between the West and Iran. The sanctions come despite Iranian President Masoud Pezeshkian and Foreign Minister Abbas Araghchi’s last-minute diplomatic efforts at the UN General Assembly this week in New York.

However, Iran’s Supreme Leader Ayatollah Ali Khamenei restricted their push by calling diplomacy with the United States a “sheer dead end.”

China and Russia’s efforts to halt the sanctions by calling for an extension of the timeframe also met a dead end. The UN sanctions will be reimposed after France, Germany and the United Kingdom triggered a “snapback” process last month, giving Iran a 30-day window to comply with their conditions or face the reintroduction of international sanctions.

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But what are these “snapback” sanctions? What else is increasing tensions between Iran and the West? We will explain.

How ‘snapback’ sanctions work

The “snapback” process, as it is called by the diplomats who negotiated it into Iran’s 2015 nuclear deal with world powers, was designed to be veto-proof at the UN Security Council and could take effect 30 days after parties to the deal told the Security Council that Iran was not complying. It would again freeze Iranian assets abroad, halt arms deals with Tehran and penalise any development of Iran’s ballistic missile programme, among other measures.

The power to impose “snapback” expires October 18, which likely prompted the European countries to use it before they lost the measure. After that, any sanctions effort would face a veto from UN Security Council members China and Russia, nations that have provided support to Iran in the past. China has remained a major buyer of Iranian crude oil, something that could be affected if “snapback” happens, while Russia has relied on Iranian drones in its war on Ukraine.

A raft of UN sanctions on Iran over its nuclear program, lifted under a landmark 2015 deal, will go back into force at the end of Saturday -- barring a diplomatic breakthrough, thought to be unlikely.https://t.co/TlfsP4JFue pic.twitter.com/R9dQiUxaIA

— AFP News Agency (@AFP) September 27, 2025

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Why Iran’s nuclear programme concerns the West

Iran has insisted for decades that its nuclear programme is peaceful. However, its officials increasingly threaten to pursue a nuclear weapon. Iran now enriches uranium to near-weapons-grade levels, the only country in the world without a nuclear weapons programme to do so.

Under the original 2015 nuclear deal, Iran was allowed to enrich uranium up to 3.67 per cent purity and to maintain a uranium stockpile of 300 kilogrammes (661 pounds). The International Atomic Energy Agency (IAEA) put Iran’s stockpile just before the war at 9,874.9 kilogrammes (21,770.4 pounds), with 440.9 kilogrammes (972 pounds) of uranium enriched up to 60 per cent. That would allow Iran to build several nuclear weapons, should it choose to do so.

US intelligence agencies assess that Iran has yet to begin a weapons programme, but has “undertaken activities that better position it to produce a nuclear device, if it chooses to do so.”

When the US hit three major Iranian nuclear sites

Iran’s nuclear facility at Natanz, located some 220 kilometres (135 miles) southeast of Tehran, is the country’s main enrichment site and had already been targeted by Israeli airstrikes when the US attacked it in June. Uranium had been enriched to up to 60 per cent purity at the site — a short step away from weapons grade — before Israel destroyed the aboveground part of the facility, according to the IAEA.

Another part of the facility on Iran’s Central Plateau is underground to defend against airstrikes. It operates multiple “cascades,” groups of centrifuges that work together to more quickly enrich uranium. The IAEA has said it believes that most if not all of these centrifuges were destroyed by an Israeli strike that cut off power to the site. The US also dropped so-called bunker-busting bombs on the site, likely heavily damaging it.

Iran’s nuclear enrichment facility at Fordo, located some 100 kilometres (60 miles) southwest of Tehran, also came under US bombardment with bunker-busting bombs. The US struck the Isfahan Nuclear Technology as well with smaller munitions.

Israel separately targeted other sites associated with the programme, including the Arak heavy water reactor.

Why Iran and the US have sour relations

Iran was decades ago one of the US’ top allies in West Asia under Shah Mohammad Reza Pahlavi, who purchased American military weapons and allowed CIA technicians to run secret listening posts monitoring the neighbouring Soviet Union. The CIA fomented a 1953 coup that cemented the shah’s rule.

But in January 1979, the shah, fatally ill with cancer, fled Iran as mass demonstrations swelled against his rule. Then came the Islamic Revolution led by Grand Ayatollah Ruhollah Khomeini, which created Iran’s theocratic government.

Later that year, university students overran the US Embassy in Tehran, seeking the shah’s extradition and sparking the 444-day hostage crisis that saw diplomatic relations between Iran and the US severed.

During the Iran-Iraq war of the 1980s, the US backed Saddam Hussein. During that conflict, the US launched a one-day assault that crippled Iran at sea as part of the so-called “Tanker War,” and later it shot down an Iranian commercial airliner that the American military said it mistook for a warplane.

Iran and the US have seesawed between enmity and grudging diplomacy in the years since, and relations peaked with the 2015 nuclear deal. But Trump unilaterally withdrew America from the accord in 2018, sparking tensions in West Asia that persist today, fanned by the Israel-Hamas war and Israel’s wider strikes across the region.

With inputs from AP