The U.S. officials, who spoke to Reuters on condition of anonymity, said one of the wounded Americans was seriously injured. The casualty count was based on initial reports which could still change, they said.
"Base personnel are conducting a post-attack damage assessment," one of the officials added.
Ismail Haniyeh, the political leader of Palestinian Islamist group Hamas, was assassinated in the Iranian capital Tehran last week, an attack that drew threats of revenge by Iran on Israel. Iran blamed Israel for the killing, but Israel has not claimed responsibility.
Coupled with the killing of the senior military commander of the Lebanese group Hezbollah, Fuad Shukr, by Israel in a strike on Beirut last week, the killings have fuelled concern the conflict in Gaza was turning into a wider Middle East war.
Iran has said the U.S. bears responsibility in the assassination of Haniyeh because of its support for Israel.
In a call on Monday, U.S. Secretary of Defense Lloyd Austin and Israeli Minister of Defense Yoav Gallant agreed that the attack marked "a dangerous escalation," according to a Pentagon readout.