As Israel launches its unprecedented military effort to eradicate Tehran’s nuclear programme by force, experts suggest only the US has the weapons capable of doing so.
Since prime minister Benjamin Netanyahu announced “Operation Rising Lion” last Friday, Israel has struck near multiple nuclear facilities, including at Natanz and Isfahan, while assassinating a host of Iran’s top military commanders and nuclear scientists.
But while the UN’s nuclear watchdog assessed on Monday that Israel has damaged sites above ground at Natanz and Isfahan, and potentially underground centrifuges at the former site, Iran’s underground facilities at Isfahan and – crucially – the Fordow enrichment plant are believed to remain unaffected.
What are bunker buster bombs?
Fordow, Iran’s most fortified nuclear site, was clandestinely built deep inside a mountain to protect it from attack. In March 2023, the UN’s International Atomic Energy Agency (IAEA) warned that it had discovered uranium enriched to 83.7 per cent purity at Fordow – close to the 90 per cent level needed to create nuclear weapons.
But despite Israel now commanding swathes of Iranian airspace, analysts say that only Washington’s arsenal contains the conventional aerial weapons capable of successfully penetrating Fordow’s mountainous shell.
That weapon is the Massive Ordnance Penetrator (MOP), a bomb six metres in length and weighing 13.6 tonnes, whose dense casings enable it to remain intact while it punches through rock and concrete before detonating deep underground.
Technically known as the GBU-57F/B, the “bunker busting” bomb is reportedly capable of reaching up to 61 metres underground before exploding – around 10 times further than the GBU-28 bunker busters owned by Israel.
However, with Iranian nuclear facilities at Fordow believed to be as deep as 80 or 90 metres underground, even the US weapons – of which Washington reportedly has around 20 in its stockpile – would potentially struggle to destroy the facility.
And it remains unlikely that the US would enter the fray directly in such a way, as doing so would significantly raise the risk to Washington’s military assets in the region and spark a destabilising conflict impacting Iran’s neighbours.
Will the US get involved in Iran?
Despite these risks, however, Donald Trump fuelled speculation of potential US involvement in the war on Monday night as he left the G7 summit in Canada early.
Contradicting claims by France’s President Emmanuel Macron, Mr Trump – who has praised Israel’s attacks on Iran as “excellent” – said his reason for leaving early “certainly has nothing to do with a ceasefire”, adding: “Much bigger than that ... Stay tuned!”
The clearest sign that the US was planning to deploy its bunker busters would be if Washington opted to move its B-2 bomber jets – the only aircraft approved to carry GBU-57F/Bs – to the UK-US military base in the Chagos Islands, The Times suggested.
US General Joseph Votel, formerly chief of the Pentagon’s Central Command during Mr Trump’s first presidential term, told the New York Times: “We’ve had a policy for a long time of not providing those to the Israelis because we didn’t want them to use them.”
Would attacks on nuclear sites endanger civilians?
Alongside the geopolitical and military risks of joining Israel in attacking a sovereign nation, the nuclear contamination from such an attack could pose a danger to civilians, warned Mr Votel.
The IAEA chief, Rafael Grossi, has issued similar warnings in recent days, stressing that “any military action jeopardising the safety and security of nuclear facilities risks grave consequences for the people of Iran, the region, and beyond”.
Urging “all parties to exercise maximum restraint to avoid further escalation”, Mr Grossi warned that nuclear facilities must never be attacked under any circumstances.
However, Israel’s ambassador to Washington, Yechiel Leiter claimed on Sunday that Israel has “a number of contingencies which will enable us to deal with Fordow”, telling ABC News: “Not everything is a matter of taking to the skies and bombing from afar.”
What other options does Israel have besides bombing?
Former US officials told the New York Times that one plan previously floated by Israel to the Obama administration suggested Israeli commandos could fight their way into the facility and blow it up from the inside – in a similar but far more dangerous operation to one successfully carried out at a Hezbollah missile production factory last year.
“The Israelis have sprung a lot of clandestine operations lately, but the physics of the problem remain the same,” US General Kenneth McKenzie Jr told the outlet, adding: “It remains a very difficult target.”
Iran has denied allegations that it is secretly developing nuclear weapons, the pretext upon which Israel began striking Iran on Friday morning. More than 200 people have been killed in Iran and more than 20 in Israel, their respective authorities have reported.
Claiming to have struck dozens of targets linked to Iran’s nuclear and ballistic missile programmes overnight, an Israeli military official told Reuters on Tuesday that the Israeli airforce had yet to target Fordow – but that this could still happen.
With the anonymous official insisting that Israel was taking precautions to avoid triggering a nuclear disaster, defence minister Israel Katz told reporters that the facility at Fordow is “an issue that will certainly be addressed”.
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