This is what you need to know about the Iran nuclear deal

Iran has announced its intention to partially withdraw from a 2015 international agreement under which it curbed its nuclear activity in return for the lifting of economic sanctions. The news comes a year after president US President Donald Trump abandoned the deal.

Despite the US pulling out and reinstating sanctions, other signatories remain committed to a deal which many see as the best way to ensure Iran cannot develop nuclear weapons.

As sanctions continue to squeeze Iran’s economy, President Hassan Rouhani issued a 60-day deadline to the remaining signatories. Unless they uphold their promise to protect Iran’s oil and banking interests, Tehran could stop exporting stocks of enriched uranium and resume higher uranium enrichment, in defiance of the agreement.

“There’s now a short window of time when other signatories of the pact, and in particular European countries, can honour the obligations. If these commitments are honoured we can guarantee the continued survival of the agreement,” Iranian Foreign Minister Mohammad Javad Zarif said.

The original deal

In 2015, Iran, the five permanent members of the UN Security Council - the US, UK, France, China and Russia – and Germany all signed up to a Joint Comprehensive Plan of Action, or JCPOA. From Iran’s side, it eased crippling sanctions, while other signatories hailed it as a diplomatic breakthrough that would make the world less dangerous.

Key points of the plan included Iran agreeing to reduce its uranium enrichment capacity by two-thirds for 10 years. Its stockpile of low-enriched uranium was cut by 96% to 300kg and capped at that level.

External inspectors from the International Atomic Energy Agency were also given access to nuclear sites, including military ones, if they suspected undeclared nuclear activities were taking place. The Arak heavy-water reactor was redesigned so it could not produce weapons-grade plutonium. Use of further heavy-water reactors was also banned for 15 years.

Once the deal was agreed and the limitations of its nuclear activities had been confirmed, international sanctions against Iran were lifted. This was meant to help the country boost its economy by regaining access to financial markets. While Iran’s GDP did improve after the lifting of sanctions, unemployment has continued to take a toll on living standards.

The International Atomic Energy Agency (IAEA), a UN body that monitors disarmament, said Iran, which is "subject to the world’s most robust nuclear verification regime", is complying with the treaty.

Why did the US withdraw?

Trump withdrew from the agreement - which had been signed under Barack Obama - in May 2018, having been a long-standing critic of it before he was elected.

He argued that the limits and inspections on nuclear activity were too weak. He also criticised its failure to deal with Iran's development of ballistic missiles.

Opponents have said so-called “sunset clauses” in the agreement, which allow Iran to recommence nuclear activities at various stages over a 15-year period, do not ensure it can never build nuclear weapons. They add that the deal places no restrictions on how Iran spends any post-sanctions revenues, including on missile development and proxy wars.

What happens next?

Since the US withdrawal, negotiations have been taking place between the remaining parties in an effort to rescue the JCPOA.

The US reacted to president Rouhani's announcement with plans to deploy an aircraft carrier and a bomber task force to the Gulf. The Trump administration has imposed new sanctions preventing Iranian exports of metals such as steel and copper, important sources of foreign revenue.

The situation has added strain on Iran’s relationship with European powers, as well as China, while deepening the divide between the US and its western allies.

Iran’s rial hit near-record lows following the US pullout last year, and the economy has continued to struggle.

Global oil prices have risen in reaction to the escalation of tensions, reflecting concerns that sanctions and geopolitical instability could curb production.