Hundreds of US troops have arrived at an air base 40 miles south of Mosul to support Iraq's efforts to liberate that city, a US defense official told CNN.
The US-led coalition to counter ISIS says it carried out four additional airstrikes near Mosul and Qayyarah Friday, destroying eight ISIS fighting positions and damaging a tunnel entrance. Near Qayyarah, two strikes engaged an ISIS tactical unit and destroyed a vehicle, a weapons cache and 29 watercraft.
Qayyarah air base was recaptured from ISIS by Iraqi soldiers backed by US airstrikes in July
and the American forces operating there will mainly provide logistics, supplies and support for the Iraqi offensive on Mosul. The move brings US personnel closer to the battle and ISIS' defensive lines.
"When the (Iraqi Security Force) is ready to move on in their operations to get after Mosul, we'll be prepared to support that and the airfield will be ready," Lt. Gen. Jeffrey Harrigian told reporters Tuesday at the Pentagon. He added that coalition forces are conducting intelligence, reconnaissance and surveillance efforts in the area.
Asked if US forces advising the Mosul operation faced increased risk, Pentagon press secretary Peter Cook told reporters Thursday that "the secretary (of defense) has made clear that our forces in Iraq are in harm's way. Everyone who is serving there is in a dangerous situation."
The air base is also expected to be rebuilt to allow US and coalition aircraft to operate there, since its proximity to Mosul makes it tactically important.
"This is a partnered effort. This is something we're working from both the land component perspective with the Iraqis and clearly ensuring that, as we begin to put some of our airplanes in there in the future, that it's got the capabilities that we need," Harrigian added, describing efforts to prepare Qayyarah.
The assault could begin as early as October, according to several US officials. The next stage of the effort to retake Mosul will involve attempts to seize towns and villages on the southern outskirts of the city.
Iraqi security forces air dropped thousands of leaflets south of the city over the weekend warning citizens in anticipation of a new offensive.
"Protect yourself, don't be human shields for the enemy, leave the town immediately," a leaflet shown by the Iraqi military to CNN said.
The coalition is stepping up airstrikes along key infiltration routes into Mosul in hopes of keeping the city from being reinforced further by ISIS, a US defense official added.
The coalition announced Friday that it had carried out airstrikes Thursday against a logistics facility in Mosul and an ISIS tactical unit in Qayyarah.
The fight for Mosul is expected to be a difficult one. Defense officials and intelligence analysts said ISIS has dug-in since it first seized the city in 2014.
There are 3,000 to 4,500 ISIS fighters in Mosul, according to Operation Inherent Resolve spokesman Col. John Dorrian.
"There is still a tough fight ahead against an adaptive enemy that will try to challenge us as we hone in on Mosul," said Harrigian, the commander of US air forces in the Middle East.