President Obama acknowledged Sunday that U.S. intelligence officials "underestimated" the threat posed by the Islamic State and overestimated the Iraqi army’s capacity to defeat the militant group.

The president said in a wide-ranging interview on CBS' “60 Minutes” that the Islamic State militants went "underground" after being squashed in Iraq and regrouped under the cover of the Syrian civil war.

"During the chaos of the Syrian civil war, where essentially you have huge swaths of the country that are completely ungoverned, they were able to reconstitute themselves and take advantage of that chaos," Obama said.

The president said his director of national intelligence, James Clapper, has acknowledged that the U.S. "underestimated what had been taking place in Syria.” He also said it was "absolutely true" that the U.S. overestimated the ability and will of the Iraqi army.

However, Obama also acknowledged that the U.S. is dealing with a conundrum in Syria, as the U.S.-led military campaign against the Islamic State is helping Syrian President Bashar Assad, whom the U.N. has accused of war crimes. 

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"I recognize the contradiction in a contradictory land and a contradictory circumstance," Obama said. "We are not going to stabilize Syria under the rule of Assad," whose government has committed "terrible atrocities."

However, Obama called the threat from the Islamic State, also known as ISIS or ISIL, and other terror groups a more "immediate concern that has to be dealt with."

"On the other hand, in terms of immediate threats to the United States, ISIL, Khorasan Group -- those folks could kill Americans," he said. 

The Islamic State group, also known as ISIS or ISIL, 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 Qaeda affiliate.

Both groups have been targeted by U.S. airstrikes in recent days; together they constitute the most significant military opposition to Assad. Obama said his first priority is degrading the extremists who are threatening Iraq and the West.  To defeat them, he acknowledged, would require a competent local ground force, something no analyst predicts will surface any time soon in Syria, despite U.S. plans to arm and train "moderate" rebels.

"Right now, we've got a campaign plan that has a strong chance for success in Iraq," the president said. "Syria is a more challenging situation."

In discussing Iraq, Obama said the U.S. left the country after the war with “a democracy that was intact, a military that was well-equipped and the ability then (for Iraqis) to chart their own course.”

However, Prime Minister Nouri al-Maliki “squandered” that opportunity over roughly five years because he was “much more interested in consolidating his Shia base and very suspicious of the Sunnis and the Kurds, who make up the other two thirds of the country,” the president said.

Obama said military force is necessary to shrink the Islamic State’s capacity, cut off financing and eliminate the flow of foreign fighters. He said political solutions are also needed that accommodate both Sunnis and Shiites, adding that conflicts between the two sects are the biggest cause of conflict throughout the world.

 Earlier Sunday, House Speaker John Boehner questioned Obama's strategy to destroy the Islamic State group. Boehner said on ABC's "This Week" that the U.S. may have "no choice" but to send in American troops if the mix of U.S.-led airstrikes and a ground campaign reliant on Iraqi forces, Kurdish fighters and moderate Syrian rebels fails to achieve that goal.

"These are barbarians. They intend to kill us," Boehner said. "And if we don't destroy them first, we're going to pay the price."

However, Obama again made clear he has no interest in a major U.S. ground presence beyond the 1,600 American advisers and special operations troops he already has ordered to Iraq. When asked if the current conflict was not really a war, Obama said there are clear distinctions between this campaign and the wars in Iraq and Afghanistan.

"We are assisting Iraq in a very real battle that's taking place on their soil, with their troops," the president said. "This is not America against ISIL. This is America leading the international community to assist a country with whom we have a security partnership."

"That's always the case," Obama added. "We are the indispensable nation. We have capacity no one else has. Our military is the best in the history of the world. And when trouble comes up anywhere in the world, they don't call Beijing. They don't call Moscow. They call us."

The Associated Press contributed to this report.