U.S. President Barack Obama on Tuesday said he was confident that Iraqi forces leading the military operations against Daesh would defeat the militant group.

"The start of Iraqi operations to liberate Mosul is another major step forward," Obama said, speaking at a White House news conference alongside Italian Prime Minister Matteo Renzi. "ISIL will be defeated in Mosul," he added, using an acronym for Daesh.

But the U.S. leader warned of a challenging road ahead.

"Mosul will be a difficult fight. There will be advances and there will be setbacks," Obama said.

"Perhaps one million civilians are still living there," Obama added. "In addition to rooting out ISIL, our focus is on the safety and humanitarian aid for civilians escaping the fight. That will be a top priority for both our governments."