President Barack Obama is acknowledging that U.S. intelligence agencies underestimated the threat from Islamic State militants in the Middle East and overestimated the ability and will of Iraq’s army to fight such extremists.

Obama described the U.S. intelligence assessments in response to a question during a CBS “60 Minutes” interview that aired Sunday, in which he also conceded that the U.S. led military campaign against that group and an al-Qaida affiliate in Syria was helping Syrian dictator Bashar Assad, a man the U.N. has accused of war crimes. But Obama said he had no choice but to order U.S. air strikes on Assad’s enemies, the Islamic State and the Khorasan Group because, he said, “those folks could kill Americans.”

The Islamic State group, which derived from but has broken with al-Qaida, has taken control of large sections of Iraq and Syria. The Khorasan Group is a cell of militants that the U.S. says is plotting attacks against the West in cooperation with the Nusra front, Syria’s al-Qaida affiliate.