President Barack Obama said Monday the U.S. military will continue airstrikes in Iraq against the Islamic State as part of a "long-term strategy" against the militants.

He also confirmed that Kurdish and Iraqi government forces had retaken the Mosul dam from IS, calling the operation a "major step forward" in the battle to undo the gains of the jihadist group, which continues to hold the city of Mosul and large swathes of territory across northern Iraq.

The United States is building an international coalition to provide humanitarian aid to Iraqis affected by the IS offensive, Obama told reporters in the White House briefing room.

The president urged Iraqi leaders to quickly grasp the opportunity created by last week's agreement to form a new, more inclusive government.

"With that new government in place, Iraqis will be able to unite the country against the threat" from IS, he said. "And they will be able to look forward to increased support, not just from the United States, but from other countries in the region and around the world."

U.S. forces mounted 15 airstrikes in northern Iraq on Monday, bringing to 68 the total number of attacks carried out over the last 11 days.

"Failure of the Mosul dam could threaten the lives of large numbers of civilians, threaten U.S. personnel and facilities - including the U.S. Embassy in Baghdad," the White House said in a letter to Congress outlining the rationale for airstrikes in support of the Iraqi-Kurdish push to retake the dam. EFE