WASHINGTON: A powerful American bunker-busting bomb is the only weapon capable of destroying Iran鈥檚 deeply buried nuclear facilities, making it President Donald Trump鈥檚 weapon of choice if he chooses to militarily back Israel.

The GBU-57, a 30,000-pound (13,607 kg) warhead capable of penetrating 200 feet (61 meters) underground before exploding, is missing from Israel鈥檚 arsenal despite its stated goal of preventing Iran from building a nuclear bomb.

In less than a week, the Israeli army has taken out Iranian military commanders and damaged numerous surface installations, raising more questions than answers.

鈥淭he regime鈥檚 missile stockpiles, launchers, military bases, production facilities, nuclear scientists, military command and control has taken a very severe beating,鈥� said Behnam Ben Taleblu, director of the Iran program at the Washington-based think tank Foundation for Defense of Democracies (FDD), a conservative-leaning group.

鈥淏ut there are still outsized questions as to how efficacious of a strike Israel had against the beating hearts of Iran鈥檚 nuclear program,鈥� Taleblu said.

The International Atomic Energy Agency (IAEA) has reported no damage at Fordo, a uranium enrichment plant south of Tehran. Unlike the Natanz and Isfahan sites in central Iran, Fordo is buried deep underground, beyond the reach of Israeli bombs.

鈥淎ll eyes will be on Fordo, which is buried under about 300 feet of rock in central Iran,鈥� Taleblu said.

Former US Army lieutenant general and Rand Corporation defense researcher Mark Schwartz insists that 鈥渙nly the United States has the conventional capacity鈥� to destroy such a site.

And by 鈥渃onventional capacity,鈥� he means the non-nuclear GBU-57 bomb.

The US military says the GBU-57 鈥� also named Massive Ordnance Penetrator 鈥� 鈥渋s designed to penetrate up to 200 feet underground before exploding,鈥� navigating through rock and concrete.

This differs from missiles or bombs that typically detonate their payload near or upon impact.

鈥淭o defeat these deeply buried targets, these weapons need to be designed with rather thick casings of steel, hardened steel, to sort of punch through these layers of rock,鈥� said Masao Dahlgren, a fellow working on missile defense for the Center for Strategic and International Studies (CSIS), a Washington-based research center.

The 6.6-meter-long GBU-57 also has a specialized fuse because 鈥測ou need an explosive that鈥檚 not going to immediately explode under that much shock and pressure,鈥� Dahlgren said.

Design for this bomb began in the early 2000s, and an order for 20 units was placed with Boeing in 2009.

The only aircraft capable of deploying the GBU-57 is an American B-2 Bomber, a stealth aircraft.

Some of these bombers were deployed in early May on Diego Garcia, the site of a joint UK-US military base in the Indian Ocean, but were no longer visible by mid-June, according to AFP鈥檚 analysis of satellite imagery provided by Planet Labs.

With their long-range capabilities, B-2s departing from the United States 鈥渁re able to fly all the way to the Middle East to do bombing runs. That鈥檚 been done before,鈥� Dahlgren said.

Each B-2 can carry two GBU-57 bombs, and Schwartz said multiple bombs will likely be needed.

鈥淭hey鈥檙e not going to just be one and done,鈥� he said.

Schwartz added that the air superiority Israel has established over Iran reduces the risks faced by the B-2 bombers.

Such a US intervention would come with 鈥渁 lot of political baggage for America,鈥� Taleblu said, emphasizing that the bunker-buster bomb is not the only way to address Iran鈥檚 nuclear program.

Without the GBU-57 bombs, and short of a diplomatic solution, Taleblu said Israelis could attack access to underground complexes like Fordo by 鈥渢rying to hit entrances, collapse what they can, cut electricity鈥� and take other measures that have already been taken at Natanz.