KHAZER, Iraq — Iraqi and Kurdish commanders said today they paused their advance on Mosul, a day after the start of a massive operation to retake the Islamic State-held city, which is expected to take weeks, if not months.

The front lines to the east of Mosul were largely quiet, a day after Iraqi Kurdish forces advanced amid a barrage of U.S.-led airstrikes and heavy artillery.

“We are just holding our positions,” said Col. Khathar Sheikhan, of the Kurdish forces known as the peshmerga, which captured a handful of villages east of Mosul on Monday. “The Iraqi army will now advance past our arenas of control.”

“We have achieved our objectives,” he said.

But an Iraqi special forces commander said his troops have delayed an advance following a request from Kurdish forces for more time to achieve their goals. It was not immediately possible to reconcile the accounts. Brig. Gen. Haider Fadhil said his men had planned to move at dawn, but postponed the operation. He said Iraqi army and Kurdish commanders would meet later today. Iraqi Prime Minister Haider al-Abadi had announced the long-awaited offensive Monday, vowing to liberate the city from more than two years of extremist rule. Mosul is Iraq’s second largest city and the IS group’s last major urban bastion in the country.