As the diplomatic push to renew ceasefire talks between the United States and Iran continues, Washington and Tehran have also been negotiating a deal on Iran’s uranium enrichment
Iran’s current stockpile of enriched uranium — and its ability to enrich further — have been central elements of the long-standing demand by the administration of US President Donald Trump that Tehran not only commit to not building a nuclear weapon, but also give up the ability to do so.
Now, according to multiple US media reports, specific differences regarding Iran’s nuclear enrichment have emerged as a critical stumbling block in negotiations between the two countries aimed at ending their war
High-powered teams from the US and Iran met in Islamabad, Pakistan, over the weekend, but failed to agree to a deal. Pakistan is attempting to get both sides to come to a second round of talks
The breakdown in talks in Pakistan over the weekend occurred over a US insistence that Iran suspend its uranium enrichment programme for 20 years in exchange for sanctions relief, followed by Tehran’s refusal to agree to a moratorium on enrichment beyond five years
So why are Iran and the US arguing over the duration of uranium enrichment? Will it impact ceasefire talks
Uranium is a naturally occurring radioactive material found in rocks, soil, and water, which, when enriched, is used as a source of fuel for nuclear reactors
It comes in the form of three natural isotopes (chemical elements that contain equal numbers of protons but different numbers of neutrons in their nuclei): uranium-234 (U-234), uranium-235 (U-235) and uranium-238 (U-238). U-235 is highly radioactive; the other isotopes are notthe
According to the United Nations’ atomic energy watchdog, the International Atomic Energy Agency (IAEA), uranium enrichment is “the process through which the isotopic proportion of U-235 is increased from 0.72 percent to up to 94 percent
The IAEA says uranium is considered low-enriched if its isotopic proportion of U-235 remains below 20 percent. This is generally used in civilian, commercial reactors to generate power for homes and industries. It is considered highly enriched if its isotopic proportion is beyond 20 percent
Enrichment needs to cross 90 percent for it to be considered weapons-grade.
Uranium also needs to be in the form of a gas to carry out the enrichment process, and most countries, including Iran, use the process of spinning uranium hexafluoride in order to enrich it. This involves feeding the gas into fast-spinning centrifuges. The lighter U-235 separates from the heavier U-238.
Currently, Iran is believed to have about 440kg (970 pounds) of uranium enriched to 60 percent – the level at which it becomes much faster to get to the 90 percent threshold needed to produce a nuclear weapon.
The useful enriched uranium-235 is then captured for nuclear fue
An unknown quantity is also believed to be stored at the Natanz facility. These two underground nuclear sites, along with a third at Fordow, were destroyed or badly damaged in US-Israeli air strikes in the 12-day war in June 2025, and have been targeted again during the current conflict
That amount is enough, theoretically, to produce more than 10 nuclear warheads, IAEA chief Rafael Grossi told Al Jazeera in early March. He added that almost half of the 60-percent-enriched uranium was probably still in an underground tunnel complex at Iran’s Isfahan nuclear facility
It is unclear whether these stockpiles are buried under rubble — and what condition the enriched uranium is in
Iran has always maintained that its uranium enrichment programme is for civilian energy purposes only, despite having enriched uranium far beyond the threshold required for that.
Israel and the US have repeatedly accused Iran of enriching uranium to develop nuclear weapons. The US and its allies, especially Europe, have slapped multiple rounds of sanctions on the country
In 2015, Iran struck a pact with world powers negotiated by then-US President Barack Obama, called the Joint Comprehensive Plan of Action (JCPOA). Under the pact, Tehran agreed to scale down its nuclear programme in exchange for relief from sanctions
Chris Featherstone, a political scientist at the University of York, told Al Jazeera that Iran is understandably interested in offering the fewest concessions to the US in their negotiations.
“For the US, they have long held the view that Iran should be prevented from obtaining nuclear weapons. As such, they want to ensure Iran commits to not enriching uranium for as long as possible. Importantly, the longer that Iran goes without enriching uranium, the more difficult it is to restart the process,” Featherstone explained
He added that for Trump, it’s also all about being able to justify his claims that he is winning the war
Iran committing to not enriching uranium for as long as possible can be seen as a ‘success’,” Featherstone said. “And he can demonstrate that he has achieved something with this war