More than a year after IS fighters overran much of Iraq and Syria, the United States and its allies are struggling to turn the tide against the extremists in an air campaign known as Operation Inherent Resolve.
The Pentagon last month said it was sending 450 additional US troops to act as advisers to help Iraqi forces seize back control of the western city of Ramadi from jihadist fighters.
Speaking to reporters after a briefing at the Pentagon on Monday, Obama warned the war "will not be quick. This is a long-term campaign."
He added that more needed to be done to train government forces and Sunni tribal fighters in Iraq, as well as moderate Syrian rebels.