Israel has revealed that some of Iran’s underground stockpile of near-bomb-grade enriched uranium survived American attacks, a senior official said.

The senior official, who spoke in confidence, said the country had begun moving toward military action against Iran’s race to build a bomb as part of a secret Iranian project, The New York Times reported.

According to the official, Israeli intelligence picked up the nuclear weapons activity soon after the Israeli Air Force killed Hassan Nasrallah, the longtime leader of Hezbollah, the Iran-backed militia in Lebanon.

The observation reportedly prompted the Israeli Prime Minister, Benjamin Netanyahu, to prepare for an attack without the help of the American government.

The U.S. had struck two of Iran’s most critical enrichment sites with 30,000-pound bunker-busting bombs.

Earlier in January, American officials said they did not believe Iran was yet racing for a weapon.

The U.S. Director of National Intelligence, Tulsi Gabbard, had once told Congress in testimony that she saw no evidence the Iranians had decided to build a weapon, a position intelligence officials reiterated in June.