About 450 more U.S. troops have arrived in Iraq in the past week to support the imminent offensive to drive ISIS from Mosul, the chief U.S. military spokesman in Baghdad said Thursday.

Air Force Col. John Dorrian, spokesman for Combined Joint Task Force-Operation Inherent Resolve, declined to give a time frame for the start of the offensive but added, “We’re going to have to get started soon” if Mosul is to be wrested from the Islamic State of Iraq and Syria by the end of this year.

Army Lt. Gen. Stephen Townsend, task force commander, appeared to suggest in a Wall Street Journal interview that the Mosul offensive could begin as early as next month to fulfill Iraqi Prime Minister Haider al-Abadi’s prediction that the strategic northwestern city would fall before the end of the year.

However, in a Pentagon briefing from Baghdad, Dorrian denied that Townsend said that the Mosul push would begin in early October.

To support the coming offensive, more than 400 additional U.S. troops have arrived since last week to boost the total number of U.S. troops in Iraq from about 4,000 to 4,460, Dorrian said. The additional troops are from the 2nd Brigade Combat Team, 101st Airborne Division, out of Fort Campbell, Kentucky.

The deployment of the 2nd BCT was announced by the Army in August. The troops are expected to be assigned to the Qayyarah West airfield about 40 miles southeast of Mosul, which is being built up as a logistics hub and forward operating base for the Mosul offensive.

Dorrian said more than eight Iraqi Security Force brigades were ready for the Mosul offensive against what is believed to be about 3,000 to 4,500 ISIS defenders.

However, the offensive is temporarily on hold while the Iraqis form and train a follow-on force to occupy the city, provide relief and defend the population, Dorrian said. The size of the follow-on force had yet to be determined, he said.

Townsend predicted a difficult fight to retake the city, Dorrian said. ISIS has held Mosul for more than two years, and “they’ve had a chance to build intricate defenses.”

Townsend, who took over the task force from Lt. Gen. Sean MacFarland three weeks ago, also has responsibility for the campaign to retake Raqqa, the self-proclaimed ISIS capital in northeastern Syria, in what Dorrian described as an “increasingly crowded battlespace” since Turkey sent troops and tanks into northern Syria late last month.

Dorrian said the task now is to “deconflict” the various opposition groups under the banner of the U.S.-backed Syrian Democratic Forces from clashing with the Turks, who have closed off the last remaining section of the border that gave ISIS access to resupply and reinforcements by foreign fighters.

The Turkish forces initially clashed with the Syrian Kurdish YPG, or People’s Protection Units, which are part of the Syrian Democratic Forces and have been the most effective rebel force against ISIS in Syria.

Dorrian said the clashes have subsided since the YPG met the Turkish demand to move east of the Euphrates River.

“We’re glad to see it’s been relatively peaceful between those two,” he said.

By Richard Sisk