According to a report from Axios, U.S. President Trump has expressed skepticism about whether the U.S. Air Force’s GBU-57A/B Massive Ordnance Penetrator (MOP)—a 30,000-pound “bunker buster”—can actually reach and destroy Iran’s heavily fortified Fordow Fuel Enrichment Plant (FFEP). Fordow, Iran’s primary site for enriching weapons-grade uranium, is believed to be buried nearly 90 meters deep within a mountain near the city of Qom in northern Iran.

Over the past few days, Trump has reportedly pressed his military advisers on the MOP’s effectiveness against Fordow. Defense officials told him they are confident the weapon would be successful, but it’s unclear whether Trump is fully convinced. “The bunker buster will work. It’s not a capabilities issue. We have the capability,” a senior U.S. official told Axios, adding, “But there’s an entire plan. It’s not just drop a bunker buster and declare victory.”

Israeli officials are increasingly confident the U.S. will eventually enter the conflict and assist in targeting Fordow. However, they maintain that Israel is prepared to act alone if necessary and could inflict significant damage on the site. One contingency being considered is a commando raid by Israeli special forces—similar to the September operation in which they destroyed an underground missile facility north of Damascus. According to a U.S. official, Israeli leaders told the Trump administration that if their bombs can’t penetrate deep enough, they might “do it with humans.”