WASHINGTON - US President Barack Obama on Tuesday said although it would be "a difficult fight," he was confident that Iraqi forces leading the military operations against Islamic State would defeat the militant group.

"The start of Iraqi operations to liberate Mosul is another major step forward," Obama said Tuesday at a White House news conference with Italian Prime Minister Matteo Renzi.

"I am confident that ISIL will be defeated in Mosul and that will be another step toward their ultimate destruction," he added. Obama predicted that there would be “advances” and “setbacks” as the military campaign goes forward.

Equally important, the president said, is preparing for any humanitarian crisis that could happen as large numbers of civilians begin to flee the violence.

“Perhaps one million civilians are still living there,” he said. “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.”

"We have put together plans and infrastructure for dealing with a potential humanitarian crisis that are as extensive as the military plans," Obama said.

US military forces are also on the ground in northern Iraq, supporting local forces in a range of capabilities, including “air support, artillery, intelligence, advisers and forward air controllers.”

There are about 5,000 American service members in Iraq and half of those could be involved in the operation which, according to US and Iraqi officials, could take weeks or even months.

Approximately 100 to 200 US Special Operations forces are already advising local units in Mosul, and they have the authority to go further into the field, according to CNN.

A few dozen are forward air controllers, who gather intelligence and call in the locations of Daesh targets for airstrikes.

"Americans are in harm's way as part of this fight," Pentagon Press Secretary Peter Cook said Monday. "It's fair to say there are Americans on the outskirts of the city."

The presence of US military personnel on the ground is the latest departure from Obama’s promise against having “boots on the ground” in Iraq.

In addition, US artillery units are striking targets from sites both north and south of the city.

Mosul, Iraq’s second largest city, fell to the Daesh terrorist group in June 2014 and has served as its de facto capital in Iraq ever since.