NORTH OF MOSUL, Iraq (Reuters) - Islamic State will put up a tough fight in the western side Mosul that remains under its control despite the losses the group suffered so far in the battle for the Iraqi, a U.S. commander said on Wednesday.

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“It is hard and hard every day here,” Colonel Patrick Work, commander of the 2nd Brigade, 82nd Airborne Division, said in an interview with Reuters TV at a brigade artillery position in northern Mosul.

“There are no guarantees certainly when you are fighting and there is no timetable, it is a determined enemy that we are up against,” he said.

The United States is providing air and ground support to Iraqi and Kurdish forces trying to dislodge the hardline group from Mosul, captured in 2014.

The offensive paused last month after the capture of the districts lying east of the Tigris river that bisects the city.

Preparations are underway to launch the offensive on the western side, which is expected be more difficult because of the density of the population and the narrow streets and alleyways through which armored vehicles cannot pass.

It is from the Grand Mosque in western Mosul that Islamic State leader Abu Bakr al-Baghdadi declared a “caliphate” over parts of Iraq and Syria. Should Mosul fall, the group is expected to stage an insurgency.

“We are putting such pressure on Daesh in the west, day in day out as we shake them and choke off their logistics, and put pressure on their command and control and attack their weapons,” Work said, using an Arabic acronym of the group.

“This entire defense in the west is under such pressure that I think there is inevitable momentum.”

Work’s brigade took over command in Mosul six weeks ago from the 2nd Brigade, 101st Airborne Division.

Artillery support will be key in the upcoming battle as it can strike in all weather, he said, adding that U.S. artillery positions were repositioned after the battle for eastern Mosul.

The U.S. military has about 5,260 troops in Iraq, 1,700 of them paratroopers from Work’s brigade.