An Israeli plan to attack the heavily fortified Fordo from the inside was deemed to be a “suicide mission” by the United States, which refused to sell Israel the materiel it felt was needed to carry out the strike, the Journal reported.

U.S. officials, according to the Journal, believed that Israel was serious about striking Iran and the Obama administration stepped up surveillance of Israeli air activity. Israel was found to be practicing “strike missions” and undetected flyovers in Iran.