Speaking to CBS News, the president said that former Al-Qaeda fighters driven from Iraq had been able to gather in Syria to form the newly dangerous "Islamic State" group.

A US-led coalition of Arab and Western allies have begun an air campaign to counter the group, hitting targets in Iraq and Syria, which Obama called "ground zero for jihadists around the world."

"I think our head of the intelligence community, Jim Clapper, has acknowledged that they underestimated what had been taking place in Syria," he said, referring to his director of national intelligence.

The comments came in advance excerpts of an interview with the "60 Minutes" news show, due to air in full later Sunday.

Obama said IS propagandists had become "very savvy" with social media and lured new recruits "who believed in their jihadist nonsense" from Europe, America and Australia, as well as from Muslim countries.

The president said that part of the solution would be military, citing the US-led strikes to deny the IS group territory and resources, but that Syria and Iraq would also have to resolve their political crises.

Although Obama admit his wrong policy in Syria made ISIL advances, he insist on aiding what he called Syria moderate armed opposition which in reality did many crime against Syrian people.

This month US congress voted to authorize the training and arming of Syrian rebels to confront the militant Islamic State, backing President Obama after he personally pleaded for support.

Newly launched airstrikes in Syria are only one piece of the puzzle in the war against the ISIL, as the U.S. military prepares to launch a complex operation to train and arm Syrian armed group who fight against ISIL and Syrian government and in some cases against each others.