US President Donald Trump says he is still weighing his options regarding United States military intervention amid escalating hostilities between Israel and Iran.

Standing on the South Lawn of the White House on Wednesday, Trump said, “The next week is going to be big,” adding that Iranian officials are eager to negotiate. However, he warned them that “it’s very late to be talking,” after they reached out to him.

Officials and experts have suggested that the US’s 30,000-pound (13,000kg) bunker buster bomb is the only weapon capable of destroying the Fordow Fuel Enrichment Plant, a facility believed to be central to Tehran’s nuclear programme and carved deep into a mountain.

The United States is the only country to possess these bombs, which it delivers using B-2 bombers. If deployed against Iran, it would represent a major shift from primarily intercepting missiles on Israel’s behalf to conducting active offensive strikes against Iran.

What are bunker buster bombs?

“Bunker buster” is a general term for bombs designed to destroy targets located deep underground that conventional bombs cannot reach.

The US military’s most powerful bunker buster is the GBU-57 Massive Ordnance Penetrator. Weighing about 30,000 pounds (13,600 kg), including a 2,700kg (6,000-pound) warhead, this precision-guided bomb is made of high-strength steel and built to penetrate up to 200 feet (61 metres) underground before exploding.

The B-2 Spirit, a US stealth bomber, is currently the only aircraft designed to deploy the GBU-57 and can carry two bunker buster bombs at a time. The US Air Force says multiple bombs can be dropped sequentially, either by the same aircraft or by several, allowing each strike to burrow deeper, amplifying the overall impact.

 

Israel also operates US-made bunker busters, including the GBU-28 and BLU-109, which are typically dropped from fighter jets such as the F-15. These weapons, however, have a much shallower penetration range and are not capable of reaching extreme depths of fortified sites like Iran’s Fordow nuclear facility. In 2024, Israel reportedly used successive BLU-109 bombs to kill Hezbollah leader Hassan Nasrallah in his underground headquarters in Beirut.

How deep is Iran’s Fordow nuclear facility?

Iran’s Fordow Fuel Enrichment Plant, located about 95km (60 miles) southwest of Tehran, is built into the side of a mountain, reportedly up to 80-90 metres (260-300 feet) underground, to survive air strikes and bunker buster attacks.

Construction of the Fordow facility is believed to have begun in about 2006, and it became operational in 2009, the same year Iran officially acknowledged it.

 

Under the 2015 Iran nuclear deal, known as the JCPOA, Iran agreed to halt enrichment at Fordow and convert the site into a research centre. However, after the US withdrew from the agreement in 2018, Iran resumed uranium enrichment at the facility. Iran has insisted its nuclear programme is for civilian purposes.

Fordow is reportedly defended by Iranian and Russian surface-to-air missile systems, though those defences may have already been targeted in Israel’s ongoing strikes.

Israeli Prime Minister Benjamin Netanyahu has framed the campaign as a mission to dismantle Iran’s missile and nuclear capabilities, describing them as an existential threat. Officials have confirmed that Fordow is a key target.

“This entire operation … really has to be completed with the elimination of Fordow,” said Yechiel Leiter, Israel’s ambassador to the United States, in an interview with Fox News.

Other nuclear sites targeted

Israel is believed to have destroyed the above-ground section of Iran’s uranium enrichment facility at Natanz, the country’s largest nuclear site.

According to the United Nations’ International Atomic Energy Agency (IAEA), the resulting power loss may have also caused damage to the underground enrichment halls at the facility.

 

Before and after satellite imagery reveals the extent of the damage at Natanz.

Israeli attacks have also damaged the Isfahan enrichment facility in central Iran.

Potential nuclear and chemical contamination

On Monday, Rafael Grossi, the head of the UN nuclear watchdog, said there was a possibility of both radiological and chemical contamination from the damaged Natanz site.

Speaking at an emergency IAEA session in Vienna, Grossi said radiation levels remain normal outside Iran’s Natanz and Isfahan nuclear sites, both of which were hit in Israeli strikes. However, he warned that ongoing military escalation increases the risk of a radiological release.

Fordow is located about 32 kilometres (20 miles) south of the city of Qom, Iran’s seventh-largest city with a population of some 1.4 million and a major religious and political centre.

 

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Trump caution on Iran strike linked to doubts over ‘bunker buster’ bomb, officials say

GBU-57 bomb.

Donald Trump has suggested to defense officials it would make sense for the US to launch strikes against Iran only if the so-called “bunker buster” bomb was guaranteed to destroy the critical uranium enrichment facility at Fordow, according to people familiar with the deliberations.

Trump was told that dropping the GBU-57s, a 13.6-tonne (30,000lb) bomb would effectively eliminate Fordow but he does not appear to be fully convinced, the people said, and has held off authorizing strikes as he also awaits the possibility that the threat of US involvement would lead Iran to talks.

The effectiveness of GBU-57s has been a topic of deep contention at the Pentagon since the start of Trump’s term, according to two defense officials who were briefed that perhaps only a tactical nuclear weapon could be capable of destroying Fordow because of how deeply it is located.

Trump is not considering using a tactical nuclear weapon on Fordow and the possibility was not presented by defense secretary Pete Hegseth and the chairman of the joint chiefs of staff Gen Dan Caine in meetings in the White House situation room, two people familiar with the matter said.

But the defense officials who received the briefing were told that using conventional bombs, even as part of a wider strike package of several GBU-57s, would not penetrate deep enough underground and that it would only do enough damage to collapse tunnels and bury it under rubble.

The defense officials were also told that to completely destroy Fordow, which Israeli intelligence estimates to go down as far as 300ft, it would likely require the US to first soften the ground with conventional bombs and then ultimately drop a tactical nuclear weapon from a B2 bomber.

The assessments were made by the Defense Threat Reduction Agency (DTRA), a component of the defense department that tested the GBU-57, as it reviewed the limitations of US military ordnance against a number of underground facilities.

Interactive

The situation underscores the complex nature of such a strike and what success would entail: dropping GBU-57s would likely set back Iran’s ability to obtain weapons-grade uranium for up to a few years, but not end the programme completely.

Spokespeople for the White House and the Pentagon did not respond to requests for comment.

Taking Fordow offline – either diplomatically or militarily – is seen as central to prevent Iran from acquiring nuclear weapons after the International Atomic Energy Agency (IAEA) found the site had enriched uranium to 83.7% – close to the 90% needed for nuclear weapons.

Any effort to destroy Fordow, would require US involvement because Israel does not possess the ordnance to strike a facility that deep or the planes to carry them.

The difficulty with using the GBU-57 to target Fordow, according to the two officials familiar with the DTRA briefing, lies in part with the characteristics of the facility which is buried inside a mountain – and the fact that the bomb has never been used in a comparable situation before.

“It would not be a one and done,” a former Dtra deputy director, retired Maj Gen Randy Manner, said of the GBU-57’s limitations, adding that Fordow could be quickly rebuilt. “It might set the program back six months to a year. It sounds good for TV but it’s not real.”

The bomb is commonly known as a “bunker buster” because it was designed to destroy underground bunkers, but it can be carried only by a B2 bomber that has air superiority and requires a solid GPS signal to lock in on its target.

While Israel has said it has established air superiority over Iran, a successful strike would still require any GPS jammers and other defenses to be taken out in advance, and for the GBU-57 to penetrate deep enough into the ground to neutralize the facility.

Interactive

Iran built the nuclear enrichment facility at Fordow underground to protect it from the threat of aerial attacks. In 1981, Israel bombed a nuclear facility near Baghdad that was located above ground in order to stop Iraq developing nuclear weapons.

In recent years, Israel has devised a variety of plans to destroy Fordow without the help of the United States. In one instance, Israel proposed loading helicopters with commandos who could fight their way into the facility and blow it up – an option that Trump has dismissed, according to people familiar with the matter.