'Snowball effect' feared as Iran prepares to surpass nuclear deal limits

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 if they chose to build one.

The United Nations says Iran has so far respected the deal's terms. But by Thursday, Iran says, it will have over 300 kilogramsof low-enriched uranium in its possession, which would mean it had broken out of the atomic accord.

Iran's UN envoy described his country's nuclear deal with world powers as being in "critical condition" and warned "Iran alone cannot, shall not and will not take all of the burdens anymore to preserve" the agreement.

"As long as illegal sanctions are in place, one cannot be expected to trust the offer for an honest and genuine dialogue," Ambassador Majid Takht Ravanchi said of talks with the United States.

European countries that are still a part of the nuclear accord face a July 7 deadline imposed by Tehran to offer a better deal and long-promised relief from U.S. sanctions, or Iran will also begin enriching its uranium closer to weapons-grade levels.

"The JCPOA is a nuclear agreement that has been working and delivering on its goals. There is also no credible, peaceful alternative," European Union UN Ambassador Joo Vale de Almeida told the 15-member UN Security Council, using the acronym for the deal's formal name, the Joint Comprehensive Plan of Action.

France's UN Ambassador Francois Delattre warned that the end of the deal "would mean a dangerous step backward, bring with it uncertainty and potentially grave consequences for the region for the non-proliferation regime and for our collective security."

"Tehran must refrain from any measure that would place Iran in breach of its commitments," he told the council.

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 U.S. 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."

Under terms of the nuclear deal, Iran agreed to have less than 300 kilogramsof uranium enriched to a maximum of 3.67 per cent. Previously, Iran enriched as high as 20 per cent,a short technical step away from reaching weapons-grade levels. It also held up to 10,000 kilograms of the higher-enriched uranium.

Stockpile limit a sliding scale, experts say

Experts who spoke to The Associated Press 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 Western concerns about its program.

At the time of the deal, which was signed by Iran, the United States, 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 non-proliferation 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,director of proliferation and nuclear policy at London's Royal United Services Institute for Defence 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."

The danger comes 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 non-proliferation 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 U.S. 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 non-compliant Iran."

Davenport says Iran's moves probably are 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."

U.S., Iran locked in standoff

A year after U.S. President Donald Trump's unilateral withdrawal from the nuclear deal, the U.S. and Iran are locked in a volatile standoff. Last week, Iran shot down a U.S. military drone, saying it violated Iranian airspace, though Washington said it was above international waters.

The U.S. has blamed Iran for mysterious explosions targeting oil tankers near the Strait of Hormuz. Tehran denied any involvement.

Trump said on Wednesday he was "not talking boots on the ground" should military action be necessary against Iran. "I'm just saying if something would happen, it wouldn't last very long," Trump told Fox Business Network.

Asked if a war was brewing, Trump said: "I hope we don't but we're in a very strong position if something should happen."

Meanwhile, Israeli 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, for now, allows UNinspectors to monitor its nuclear facilities via in-person checks and surveillance cameras. It also has yet to begin widespread use of advanced centrifuges that would speed its 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 dropping.

"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."