On Sunday, September 28, 2025, the United Nations officially reinstated its sanctions on Iran concerning its nuclear program. This decision places significant renewed pressure on Tehran amidst already heightened tensions across the broader Middle East, particularly due to the ongoing conflict between Israel and Hamas in Gaza.
Just days prior, at the UN General Assembly in New York, Iranian President Masoud Pezeshkian and Foreign Minister Abbas Araghchi made a desperate, last-minute diplomatic plea to prevent these sanctions from being reimposed. However, these efforts were undermined by Iran’s Supreme Leader, Ayatollah Ali Khamenei, who publicly dismissed diplomacy with the United States as a “sheer dead end.” Adding to Iran’s woes, attempts by China and Russia to block the sanctions at the UN Security Council also failed on Friday, September 19.
The 30-day countdown to the sanctions began on August 28, 2025, after France, Germany, and the United Kingdom jointly declared that Iran was not adhering to the terms of the 2015 nuclear agreement with world powers. Tehran has consistently argued, albeit unsuccessfully, that the entire deal became null and void when the United States unilaterally withdrew from the agreement in 2018 during President Donald Trump’s first term.
Since the U.S. withdrawal, Iran has drastically limited inspections by the International Atomic Energy Agency (IAEA), the UN’s nuclear watchdog. This restriction intensified significantly following a 12-day conflict initiated by Israel against Iran on Friday, June 13, 2025, during which both the U.S. and Israel reportedly bombed critical Iranian nuclear facilities.
Despite the existing strain on Iran’s economy, Mr. Araghchi stated in New York on Friday, September 26, that he believed the sanctions would not diminish “the people of Iran’s determination to defend their rights.” He added, “The question is, what does it impact in diplomacy. It closed the way of diplomacy.”
To fully understand the current situation, let’s explore Iran’s nuclear facilities, the mechanics of ‘snapback’ sanctions, and the broader factors fueling the escalating tensions between Iran and Western nations.
Understanding ‘Snapback’ Sanctions: How They Function
The ‘snapback’ mechanism, a unique feature negotiated into Iran’s 2015 nuclear agreement, was engineered to bypass any vetoes at the UN Security Council. It was activated 30 days after signatory nations formally reported Iran’s non-compliance to the Security Council. This action has resulted in the re-freezing of Iranian assets held abroad, a ban on arms transactions with Tehran, and penalties for any advancements in Iran’s ballistic missile program, among other restrictions.
The authority to trigger these ‘snapback’ sanctions was set to expire on October 18, a deadline that likely spurred European nations to act before losing this crucial enforcement tool. Beyond that date, any new sanction attempts would have almost certainly been vetoed by UN Security Council members China and Russia, both of whom have historically supported Iran. China, a significant importer of Iranian crude oil, could see its trade impacted by these new measures, while Russia has increasingly relied on Iranian drones in its conflict with Ukraine.
Why Iran’s Nuclear Program Alarms Western Nations
For decades, Iran has maintained that its nuclear program is solely for peaceful purposes. However, Iranian officials have increasingly hinted at pursuing nuclear weapons. Currently, Iran enriches uranium to near-weapons-grade purity, a highly unusual step for any nation without an acknowledged nuclear weapons arsenal.
The initial 2015 nuclear agreement permitted Iran to enrich uranium to 3.67% purity and maintain a stockpile of 300 kilograms (661 pounds). However, prior to the recent conflict, the IAEA reported Iran’s uranium stockpile at a staggering 9,874.9 kilograms (21,770.4 pounds), including 440.9 kilograms (972 pounds) enriched to 60%. This quantity and purity would theoretically enable Iran to develop several nuclear weapons if it decided to.
U.S. intelligence agencies currently believe Iran has not yet initiated a nuclear weapons program. However, they note that Iran has “undertaken activities that better position it to produce a nuclear device, if it chooses to do so.” During Israel’s recent conflict with Iran, the U.S. reportedly attacked three significant Iranian nuclear sites. The Natanz facility, Iran’s primary enrichment site located approximately 220 kilometers (135 miles) southeast of Tehran, had already been hit by Israeli airstrikes before the U.S. attacks in June.
According to the IAEA, uranium at Natanz was being enriched to 60% purity – a level very close to weapons-grade – before Israeli forces destroyed the facility’s above-ground section. An underground section of the facility on Iran’s Central Plateau, designed to withstand airstrikes, housed numerous “cascades” – interconnected groups of centrifuges used for rapid uranium enrichment. The IAEA estimates that most, if not all, of these centrifuges were destroyed by an Israeli strike that disrupted power to the site. Additionally, U.S. forces reportedly deployed “bunker-busting” bombs, causing probable severe damage.
Iran’s Fordo nuclear enrichment facility, situated about 100 kilometers (60 miles) southwest of Tehran, was also hit by U.S. bunker-busting bombs.
The U.S. also attacked the Isfahan Nuclear Technology site with smaller munitions. Separately, Israel targeted other facilities linked to the program, such as the Arak heavy water reactor.
A Troubled History: The Strained Relationship Between Iran and the U.S.
Decades ago, under Shah Mohammad Reza Pahlavi, Iran was a key U.S. ally in the Middle East. The Shah acquired American military hardware and permitted CIA technicians to operate clandestine listening posts aimed at monitoring the neighboring Soviet Union. A 1953 CIA-backed coup played a pivotal role in solidifying the Pahlavi dynasty’s power.
However, by January 1979, a terminally ill Pahlavi fled Iran amidst widespread public protests against his regime. This paved the way for the Islamic Revolution, led by Grand Ayatollah Ruhollah Khomeini, which established Iran’s current theocratic government.
Later that year, university students stormed the U.S. Embassy in Tehran, demanding the extradition of the Shah. This event ignited the infamous 444-day hostage crisis, which led to the complete severing of diplomatic relations between Iran and the U.S.
During the Iran-Iraq War in the 1980s, the U.S. supported Saddam Hussein. In the course of this conflict, the U.S. carried out a significant one-day naval assault, severely impacting Iran’s maritime capabilities as part of the “Tanker War.” Subsequently, the American military tragically shot down an Iranian commercial airliner, claiming it had mistakenly identified it as a warplane.
In the decades that followed, Iran and the U.S. have experienced a tumultuous relationship, oscillating between outright hostility and reluctant diplomatic engagement. Their relations reached a high point with the 2015 nuclear deal. However, President Trump’s unilateral withdrawal from the agreement in 2018 reignited regional tensions, which continue to be inflamed by the Israel-Hamas conflict and broader Israeli military actions across the Middle East.