Obama: 'Mosul will be a difficult fight'

US President Barack Obama (R) and Italian Prime Minister Matteo Renzi conduct a joint press conference at the White House in Washington, DC, October 18, 2016 (AFP Photo/Nicholas Kamm )

Washington (AFP) - President Barack Obama warned Tuesday of a tough battle ahead as Iraqi forces backed by a US-led coalition advance on Mosul to wrest the city from the Islamic State group.

Obama said he was confident the offensive on the northern city, now in its second day, would succeed in driving the jihadists from their last stronghold in Iraq.

"There will be ups and downs in this process, but my expectation is that ultimately it will be successful," he told a joint news conference with Italian Prime Minister Matteo Renzi.

"This will be, I think, a key milestone in what I committed to doing when ISIL first emerged," Obama said, using an acronym for the jihadist group.

"We are going to roll them back, and we are going to ultimately drive them out of population centers," he vowed.

Obama said he was "confident that ISIL will be defeated in Mosul and that will be another step toward their ultimate destruction."

But the US leader warned of a challenging road ahead.

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

"Perhaps one million civilians are still living there," he 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."

Obama said he expected "significant displacement" of civilians from Mosul, and that the US-led coalition, in conjunction with the United Nations and major aid organizations was prepared to respond to it.

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