Here are key restrictions imposed on Iran under JCPOA and measures it has taken to suspend compliance.

Iran is taking a significant new step in reducing its commitments to a landmark nuclear deal following the United States‘s pullout last year, with President Hassan Rouhani announcing it will begin injecting uranium gas into more than 1,000 centrifuges at the underground Fordow plant as of Wednesday.

The centrifuges previously spun empty without gas injection under the Joint Comprehensive Plan of Action (JCPOA) negotiated between Iran and world powers in 2015.

It was one of the many restrictions imposed on Iran with the aim of extending the time the country would need to produce a nuclear bomb – if it chose to – to a year from roughly two to three months. In exchange for compliance, Iran was offered relief from global sanctions.

However, with US President Donald Trump‘s decision last year to abandon the agreement and reinstate punishing sanctions against Iran, including on its oil and banking sectors, Tehran has begun a phased suspension of its obligations.

The resumption of atomic activity at Fordow is the fourth move announced by Iran since May, a year after the US pullout.

The moves are aimed at trying to pressure the remaining signatories – the United Kingdom, France, Germany, China and Russia – to deliver on JCPOA’s promised economic benefits.

Here are the key restrictions imposed on Iran under the landmark nuclear deal and the status of its compliance.

Uranium enrichment level

The biggest obstacle to producing nuclear weapons is obtaining enough fissile material – weapons-grade highly-enriched uranium or plutonium – for the bomb’s core.

The deal capped the level of purity to which Iran can enrich uranium hexafluoride, the feedstock for centrifuges, at 3.67 percent, far below the 90 percent of weapons-grade. The cap was well below the 20 percent level at which Iran enriched uranium before the deal. It was to last 15 years.

In July, the International Atomic Energy Agency (IAEA), the United Nations agency tasked with monitoring Iran’s compliance, said Tehran cranked up uranium enrichment to 4.5 percent purity at the Natanz facility.

Uranium stockpile

The deal capped Iran’s stock of low-enriched uranium at 300 kilogrammes (661 pounds) of uranium hexafluoride enriched to 3.67 percent or its equivalent for 15 years. That corresponds to 202.8kg (447.1lb) of uranium.

The IAEA said Iran’s total enriched uranium stockpile as of August was at 241.6kg (531.3lb).

Advanced centrifuges

JCPOA also slashed the number of centrifuges installed in Iran to roughly 6,000 from about 19,000 before the deal, and only allowed Iran to produce enriched uranium with its first-generation IR-1 centrifuges.

In September, the IAEA said Iran had begun installing advanced centrifuges at Natanz after Rouhani declared Tehran will no longer abide by the agreement’s restrictions on atomic research and development.

Prior to that, Natanz had 5060 IR-1 centrifuges at the facility, the agency said.

Ali Akbar Salehi, head of the Atomic Energy Organisation of Iran, said on Monday the country doubled the number of its advanced IR-6 centrifuges in operation. Such machines can produce enriched uranium 10 times faster than the IR-1s.

Salhi also said Iran is working on a prototype that is 50 times faster than those allowed by the deal.

Fordow facility

The deal turned Fordow, one of Iran’s two enrichment sites, into a “nuclear, physics and technology center” where centrifuges are used for purposes other than enrichment, like producing stable isotopes for medical purposes.

Rouhani’s latest announcement on injecting uranium gas into the 1,044 IR-1 centrifuges at Fordow means the plant will become an active atomic site rather than a research facility.

Plutonium track

In 2016, Iranian authorities removed the core of the Arak heavy-water nuclear reactor and filled it with concrete to make it unusable. Heavy water can be employed in reactors to produce plutonium, another fuel used in nuclear warheads.

The Arak facility could eventually have produced spent fuel from which plutonium could be separated.

The IAEA, in an August report, said Iran has not pursued the construction of the Arak reactor and continued to maintain its stock of heavy water below the 130 tonnes set by JCPOA.

In July, Salehi told Iranian legislators that Iran intends to restart activities at Arak. But he did not give a date.

IAEA oversight

JCPOA grants the IAEA wide-ranging inspection powers, including daily access to Natanz and Fordow for 15 years. In its August report, the IAEA said Tehran continues to allow the agency to monitor the two sites.