The move comes days after it was confirmed that the country has also exceeded the deal's limit on its stockpile of enriched uranium.

- What does stockpile limit breach mean? -

Iran's breach of its stockpile limit currently does not mean a great deal in terms of any potential nuclear weapons development.

While Iran has always insisted its nuclear programme is peaceful, the 2015 Joint Comprehensive Plan of Action (JCPOA) froze the so-called "breakout time" Tehran needs to produce enough fissile material to make an atom bomb to one year.

The UN nuclear watchdog, the International Atomic Energy Agency (IAEA), confirmed Tehran's claim Monday that it had exceeded the uranium limit by just over two kilograms.

The limit for enriched uranium stockpiles in the JCPOA is 300kg, and experts say Iran would need several times this amount before it would be able to even start obtaining the material for a bomb.

- What about the enrichment level? -

Under the JCPOA, Iran is only meant to enrich uranium to the level of 3.67 percent -- sufficient for power generation but far below the more than 90-percent level required for a nuclear warhead.

Former IAEA inspector Robert Kelley says that once the 3.67-percent cap is breached, enriching to higher purities becomes much easier because most of the effort is spent at the beginning of the process.

"If you do enrich to 3.5 percent, you've done half the work it takes to get the rest of the way, and if you go up to 20 percent, you're up to around 80 percent of the work," he told AFP.

According to Olli Heinonen, the IAEA's former head of safeguards, Iran could offer several justifications for enriching to levels beyond 3.67 percent, including supplying its research reactor in Tehran or producing medical isotopes.

- What about the Arak reactor? -

Iran has also said it will resume building a heavy water reactor in Arak in central Iran, a project that had been mothballed under the JCPOA.

In theory, once operational, it would eventually be capable of producing plutonium, the alternative to uranium for a nuclear weapon.

David Albright from the Institute for Science and International Security think thank says such an action "would be very serious and a major impetus for the E3 (the European parties to the JCPOA) to snap back sanctions, but it would take Iran several years to finish the reactor and produce plutonium."

Iran has stressed that all the breaches announced so far could be reversed "in hours" if the other parties to the nuclear deal make good on their side of the bargain -- relief from sanctions.

- Which moves would cause more alarm? -

A key factor is whether Iran moves to ramp up centrifuge installation, particularly of more advanced models such as the IR-2M. More than 1,000 of these were removed from Natanz and put into storage under the JCPOA.

Prior to the deal, Iran had around 20,000 centrifuges of various kinds and amassed some 8,000kg of low-enriched uranium.

If the IR-2Ms were redeployed, they could bring the time needed for enriching weapons-grade uranium down to seven months, according to Albright.

However, Kelley says the "breakout" concept is misleading if it only focuses on Iran's stocks of nuclear material.

"You have to go back and say: 'Where are they in the process of high explosives, machining'," Kelley says, adding that he believes Iran is currently "deficient" in these areas.

Iran would also have to test and procure various equipment -- activities that should be detectable, Kelley said.