The White House admitted Thursday that a January US operation against an Al Qaeda compound near the Afghan-Pakistan border killed one American and one Italian hostage, along with an American member of the jihadist group.
Another American, Al-Qaeda spokesman Adam Gadahn, was killed, "likely in a separate US government counterterrorism operation."
"No words can fully express our regret over this terrible tragedy," the White House said, revealing the previously classified finding. The president "takes full responsibility for these operations."
Obama is scheduled to make a public address at 14:00 GMT (10:00 ET).