(AP) - President Barack Obama says U.S. intelligence agencies underestimated the threat from Islamic State militants and overestimated the ability and will of Iraq's army to fight. In an interview on "60 Minutes" on CBS, Obama says militants who had gone "underground" after being squashed in Iraq were able to reconstitute themselves amid the chaos of the Syrian civil war. Obama says the situation calls for both military and political solutions. He says military force is necessary to shrink their capacity, cut off financing and eliminate the flow of foreign fighters. But he says political solutions are also needed that accommodate both Sunnis and Shiites. He says conflicts between the two sects are the biggest cause of conflict throughout the world. Obama is also acknowledging that the U.S.-led military campaign against the Islamic State group and al-Qaida's affiliate in Syria is helping Syrian President Bashar Assad. But, according to the president, "in terms of immediate threats to the United States, ISIL, Khorasan Group - those folks could kill Americans." ISIL is an alternative acronym for the Islamic State group, which 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. Both groups have been targeted by U.S. airstrikes in recent days; together they constitute the most significant military opposition to Assad, whose government the U.S. would like to see gone.