WASHINGTON, Oct. 26 (Xinhua) -- The U.S. military is confident that Iraqi forces will succeed in retaking Mosul from the Islamic State (IS) as they continue to make steady progress, the military said on Wednesday.

Stephen Townsend, commander of the Combined Joint Task Force Operation Inherent Resolve, told a Pentagon briefing via teleconference from Baghdad that Iraqi forces "had developed a lot of momentum over the past two years."

"The Mosul offensive is a large and extraordinarily complex operation that the Iraqis have been planning for a very long time," Townsend said, referring to the battle launched by Iraqi forces on Oct. 17 to liberate Mosul, Iraq's second largest city.

Iraqi forces are moving forward on multiple axes toward Mosul, but the effort to take back the city will not be easy, he said.

"There's a lot of hard fighting ahead but we're confident the Iraqis will be successful," Townsend said.

The U.S.-led coalition has supported Iraqi forces in planning and preparing for the battle, by providing advice, training and assistance that includes air and artillery strikes.

The relentless campaign of strikes had removed many IS fighters, key leaders and weapons from the battlefield ahead of the battle.

Meanwhile, Townsend said that the battle to retake the Syrian city of Raqqa from IS will be launched soon. He declined to disclose further details.

The U.S. commander added that as Syria is a complicated battlespace with many regional security concerns, the battle to liberate Raqqa is going to be a tough one.

It will be different from that in Mosul, Townsend said, noting it will be done by local partnered forces, rather than a nation's armed forces.