Secretary of State John Kerry raised the specter of using a 30,000-pound (13,600-kg) bunker-buster bomb  against Iran’s nuclear program in an interview aired this week, during an attempt to reassure Israelis that America had its back against Tehran, even if it means preemptive military action.

People in Israel should have some confidence in an “administration that designed and deployed the weapon that has the ability to deal with Iran’s nuclear program,” Kerry told Channel 10, adding that his is “an administration, a government, a country that will stand by Israel way into the future.”

The weapon he was referring to, the Massive Ordnance Penetrator, or MOP, is a 30,000-pound bomb that was made operational in 2011 and recently redesigned in terms of guidance and penetration. The massive weapon has not been offered to Israel for purchase.

The US Department of Defense invested $330 million to develop 20 of the bombs and requested an additional $82 million to enhance their efficacy, the Wall Street Journal reported in 2012.

In April the Journal reported that the upgraded bomb was tested in mid-January, when it was dropped from a B-2 bomber that took off from Whiteman Air Force Base in Missouri.

The successful test showed a massive bomb that could be guided much like smaller precision weapons and was upgraded with electronic countermeasures that protect it from potential Iranian jamming, which could otherwise be used to steer incoming weaponry off target.

The US officials, who were reportedly not involved in the administration’s negotiations with Iran, told the Wall Street Journal that the bombs, if used, would have a devastating effect never before seen by a non-nuclear weapon.

The bombs are designed to be released in pairs, with the first burrowing through the layers of rock and steel that protect underground nuclear facilities like the one in Fordo, Iran, and the second to follow immediately on its heels and destroy the target.

The Journal reported that Pentagon officials have shared details about the bomb with Israeli counterparts, and have “shown them videos of the weapon hitting a target during testing.”

The videos reportedly showed a deep bunker utterly destroyed by a precision-guided bomb.

“The Pentagon,” officials told the Journal, “continues to be focused on being able to provide military options for Iran if needed,” and stressed that “if you say all options are on the table, you have to have something on the table that’s credible.”

Kerry, in the Israeli television interview, seemed to be indicating that the threat of US military action still hovers over the negotiations and acts as a stick to prevent future Iranian violations of any would-be agreement.

Official Israel, which was chastised for its preemptive action against Saddam Hussein’s nuclear reactor in 1981, and which witnessed the US’s unwillingness to act in order to thwart North Korea and Syria, remains unconvinced that the emerging deal will thwart Iran’s nuclear drive to nuclear weapons, though Kerry said he could “guarantee” this was the case.

“Now there are those who say that the Lausanne framework will make Israel safer,” Prime Minister Benjamin Netanyahu said in a video address to the Washington Institute for Near East Policy on Friday. “As the prime minister of Israel, I can tell you categorically this deal will endanger Israel — big time.”