A 13,600-kg bomb, the GBU-57 Massive Ordnance Penetrator (MOP), is the weapon that can achieve Israeli Prime Minister Benjamin Netanyahu’s stated goal of attacking Iran – eliminating Tehran’s missile and nuclear programmes.

Netanyahu has made it clear he wants US support against Iran’s nuclear ambitions, calling it an “existential threat” to his country.

"We're not just fighting our enemy. We're fighting your enemy,” he told ABC News on Monday. “For God's sake, they chant, "death to Israel, death to America." We're simply on their way. And this could reach America soon.”

But Israel cannot destroy Iran’s underground nuclear facilities without the US. Only Washington has the GBU-57 bomb that is designed to demolish such heavily fortified structures buried deep within the ground, as well as the B-2 bombers that are the only aircraft that can carry and deploy this specialised bomb.

America began designing the massive bunker buster in 2004 specifically keeping the mountains protecting some of the deepest nuclear facilities in Iran and North Korea in mind, The New York Times reported. It was tested during Donald Trump’s first term and added to the arsenal.

“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,” Gen. Joseph Votel, commander of US Central Command during Trump’s first term, told The New York Times.

Netanyahu has long wanted the bunker buster, but it now boils down to Trump.

In the US Republican camp, giving Israel the bunker buster has the support of the old-school who want the US to be the globe’s policeman, but not large sections of the MAGA bunch who are more isolationist in their foreign-policy views. .

The old-school hawkish US Senator Lindsey Graham on Sunday said that if the diplomatic efforts failed with Iran, he would urge Trump “to go all in to make sure that, when this operation is over, there’s nothing left standing in Iran regarding their nuclear programme”.

“If that means providing bombs, provide bombs – whatever bombs. If it means flying with Israel, fly with Israel.”

On the other end of the spectrum is America’s equivalent of Arnab Goswami, one-time Fox News star turned podcaster Tucker Carlson, who wants the US to let countries like Israel “fight their own wars”.

Fordo and Natanz: Key conflicts

Key to achieving Israel’s objective is eliminating the Fordo fuel enrichment facility, buried deep underground in a glen between the Hasan Aqa and Furdu peaks around 202 km south of Tehran. It is 30 km from Qom, a petroleum distribution hub.

Israel did not target Fordo in the initial strikes, but there were strikes in subsequent rounds of attacks. On Monday, Israel reportedly struck the main highway between Tehran and Qom. The International Atomic Energy Agency (IAEA) said on Monday that there is no damage visible at the Fordo site.

The other key nuclear facility is Natanz, 300 km south of Tehran and on the main north-south highway of Iran. The city that is 1,666 metres above sea level houses two uranium enrichment complexes and reportedly has an underground facility under construction.

Israel struck Natanz on June 13. The IAEA has said Israeli strikes had 'direct impacts' on Natanz’s underground centrifuge halls. The New York Times said the Israeli attack took out power to the site.

IAEA director general Rafael Grossi said Monday that while buildings above the ground at the Natanz facility had been destroyed, strategic locations underground had not been struck.

“There has been no indication of a physical attack on the underground cascade hall containing part of the pilot fuel enrichment plant and the main fuel enrichment plant,” Grossi said.

Trump card

The GBU-57, the bomb that can destroy both these facilities, can only be deployed by B-2 bombers, of which only 19 are in service in the US Air Force. In April, six to seven B-2s were moved to the Diego Garcia base in the Indian Ocean, each with the capacity to carry two of these GBU-57s.

“I think Iran basically is at the negotiating table, they want to make a deal,” Trump, who returned to Washington abruptly from the G-7 summit in Canada, said Monday. He iterated that Tehran “cannot have a nuclear weapon”.

In Canada, he had said he wanted “an end, a real end, not a cease-fire.”