As Iran prepares to surpass limits set by its 2015 nuclear deal with world powers, each step it takes narrows the time the country's leaders would need to have enough highly enriched uranium for an atomic bomb.
The United Nations says Iran has so far respected the deal's terms. But by Thursday, Iran says it will have over 300 kg (660 lbs) of low-enriched uranium in its possession, which would mean it had broken out of the atomic accord.
Follow Israel Hayom on Facebook and Twitter
European countries that are still a part of the nuclear accord will face a July 7 deadline imposed by Tehran to offer a better deal and long-promised relief from US sanctions, or Iran will also begin enriching its uranium closer to weapons-grade levels.
Breaking the stockpile limit by itself doesn't radically change the one year experts say Iran would need to have enough material for a bomb. Coupled with increasing enrichment, however, it begins to close that window and hamper any diplomatic efforts at saving the accord.
"I worry about the snowball effect," said Corey Hinderstein, a vice president at the Washington-based Nuclear Threat Initiative who once led the US Energy Department's Iran task force. "Iran now takes a step which puts Europe and the other members of the deal in an even tougher position," he said.
Under the terms of the nuclear deal, Iran agreed to have less than 300 kg (660 lbs) of uranium enriched to a maximum of 3.67%. Previously, Iran enriched as high as 20%, which is a short technical step away from reaching weapons-grade levels. It also held up to 10,000 kg (22,040 lb) of the higher-enriched uranium.
Experts described the enrichment and stockpile limits in the deal as a sort of sliding scale. Balancing both elements keeps Iran a year away from having enough material for a nuclear weapon, something Iran denies it seeks despite concerns about its program.
At the time of the deal, which was agreed to by Iran, the US, China, Russia, Germany, France and Britain, experts believed Iran needed anywhere from several weeks to three months to have enough material for a bomb.
However, the stockpile limit isn't an immediate worry from a nonproliferation standpoint, experts say.
"Going over the limit doesn't immediately signify that Iran has enough material that could – if further enriched and processed – be used in a nuclear weapon," said Tom Plant, the director of proliferation and nuclear policy at London's Royal United Services Institute for Defense and Security Studies.
"It does mean that it builds up reserves of material that could in the future support a more rapid push to the higher levels of enrichment that are suitable for weapons use," Plant said.
The danger comes on July 7, if Iran begins enriching uranium to higher levels.
"If Iran begins stockpiling uranium enriched to higher levels, the breakout timeline would decrease more quickly," said Kelsey Davenport, director of nonproliferation policy at the Washington-based Arms Control Association.
Both Davenport and Ian Stewart, a professor at King's College London who runs its anti-proliferation studies program called Project Alpha, worry about miscalculations from Iran, the US or the West amid the brinksmanship.
"This highlights the real tension at play in Iran: doing enough to satisfy Iranian hard-liners while also maintaining EU, Chinese and Russian support" for the deal, Stewart said. "There's a real risk of miscalculating, not least because it's not clear at which point the EU will have to back away from a noncompliant Iran."
Davenport says Iran's moves are likely aimed at gaining leverage in negotiations.
"Even if Iran decided to pursue a nuclear weapon, it would still take months to further enrich and weaponize the uranium," she said. "It is critical that the United States does not overreact to a stockpile breach and use it as an excuse to further ratchet up tensions in the region."
A year after US President Donald Trump's unilateral withdrawal from the nuclear deal, Washington and Tehran are already locked in a volatile standoff. Last week, Iran shot down a US military drone, claiming it violated Iranian airspace, though Washington said it was above international waters. The US has blamed Iran for mysterious explosions targeting oil tankers near the Strait of Hormuz, however, Tehran has repeatedly denied any involvement.
Meanwhile, Prime Minister Benjamin Netanyahu has vowed to stop Iran from obtaining a nuclear weapon. Israel has bombed nuclear facilities in Iraq and Syria in the past and reportedly pushed for a similar strike in Iran prior to the 2015 deal.
Iran has allowed UN inspectors to monitor some of its nuclear facilities via in-person checks and surveillance cameras. It also has yet to begin widespread use of advanced centrifuges that would speed up enrichment. Experts fear either of those happening.
Once Iran starts going beyond the terms of the nuclear deal, one fact remains indisputable: The time it needs to have enough material for a possible atomic bomb starts decreasing.
"As soon as they go over 300 or above 3.67, that number is starting to count down from one year," Hinderstein warned. "So if they do both, then it's just going to steepen that line from one year to wherever they end up."
On Wednesday, Iran warned the UN Security Council it would no longer be burdened with preserving the 2015 deal as European states pushed Tehran to stick with the agreement because there is "no credible, peaceful alternative."
"The US withdrawal from the JCPOA and reimposition of its sanctions rendered the JCPOA almost fully ineffective," Iran's UN Ambassador Majid Takht Ravanchi told the 15-member Security Council, using the acronym for the deal's formal name, the Joint Comprehensive Plan of Action.
"Iran alone cannot, shall not and will not take all of the burdens any more to preserve the JCPOA," he said.
EU Ambassador to the UN Joao Vale de Almeida warned the Security Council, "The JCPOA is a nuclear agreement that has been working and delivering on its goals. There is also no credible, peaceful alternative."
The nuclear deal is endorsed in a 2015 Security Council resolution. UN Secretary-General Antonio Guterres reports every six months on the implementation of that resolution, which also subjects Iran to an arms embargo and other restrictions.
Acting US Ambassador to the UN Jonathan Cohen described Iran's actions as "deeply counterproductive."
"Iran's defiance of the Security Council and its reckless behavior threatening peace and security globally must not be downplayed in the name of preserving a deal that doesn't fully cut off Iran's path to a nuclear weapon," he said.
He noted that the UN resolution endorsing the nuclear deal "provides a mechanism for the council to address significant non-performance of Iran by its nuclear commitments."
Under the nuclear deal, there is a process culminating at the UN Security Council that can trigger a so-called snapback of all sanctions if Iran violates the agreement.
Iran's UN Ambassador Majid Takht Ravanchi told reporters on Monday: "The US is not in a position to spark snapback because they are not part of the deal."
French UN Ambassador Francois Delattre warned that the end of the deal "would mean a dangerous step backward" and urged Tehran not to breach the deal.
Russian UN Ambassador Vassily Nebenzia said Moscow wanted Iran to remain committed to the nuclear deal, but also accused the United States of sending mixed signals.
"We hear assertions that nobody is planning regime change in Iran and then at the same time we hear threats about obliteration and new sanctions are being introduced, there are calls for dialogue and then in parallel openly they declare the intention to increase military presence in the region," he said.
"Such signals, which even an experienced cryptologist would struggle to decode, can only bring the situation to a point of no return," Nebenzia said.
