WASHINGTON — U.S.-backed ground forces have paused their advance on Iraq’s second largest city to regroup and clear pockets of Islamic State militants from dozens of villages assaulted during the battle’s first 12 days, a U.S. military spokesman said Friday.

The march of Iraqi security forces and the Kurdish peshmerga fighters toward Mosul, the Islamic State group’s final stronghold in Iraq, should continue within a few days, said Air Force Col. John Dorrian, the Baghdad-based spokesman for the U.S.-led Operation Inherent Resolve coalition. The temporary pause will allow the forces to regroup and adjust to the tactics that enemy fighters have displayed through the opening phase of the assault, he said.

“They have a plan for how far they want to get each day, and they were able to get to those places faster than they anticipated that they would,” Dorrian told reporters Friday at the Pentagon. “The Iraqis continue to be successful in the engagements against [the Islamic State group] and, essentially, they are on plan and ready to move back toward Mosul within the next couple of days.”

Iraqi and peshmerga fighters have advanced within about five miles of Mosul’s city limits in some areas, primarily to the north and east. From the south, Iraqi security forces have moved within about 10 miles of the city, according to the Pentagon.

The operation has seen a mix of tactics from the Islamic State group militants. In some areas, enemy fighters have launched fierce assaults on the Iraqi and peshmerga troops. In other areas, the militants have relied on suicide attacks and roadside bombs to attempt to halt the Iraqi ground forces or to distract them as the Islamic State fighters retreat.

With the backing of the U.S.-led coalition’s air and artillery support, ground forces have killed nearly 1,000 Islamic State fighters since the operation launched Oct. 17, said Army Gen. Joseph Votel, the Central Command chief, according to Agence France Presse. Pentagon officials have said the terrorist group still has between 3,000 and 5,000 fighters within Mosul, where it expects the militants will mount a brutal urban fight in an attempt to retain the city that they captured in June 2014.

The coalition has dropped more than 2,500 ordinance from warplanes, artillery pieces and rocket launchers during the operation, Dorrian said. They’ve destroyed at least 46 tunnels dug by the Islamic State group, 33 truck and car bombs, and hundreds of other vehicles and fighting positions.

In one case, the coalition destroyed more than 40 vehicles amassed outside of Mosul that officials believe were being staged to carry captured civilians into the city to be used as human shields, Dorrian said.

That is a tactic that the Islamic State group has used previously in Iraq and Syria. The United Nations reported this week that the terrorists have abducted “tens of thousands” of civilians in and around Mosul to use as human shields.

Dorrian said he could not confirm the U.N. figures, but he said the United States and Iraqis have long expected the group to use civilians as shields.

“They’ve done it in recent battles and here as they fall back into the city, apparently they are taking some of the local residents as human shields,” he said. “This is something we try to stop when we can.”

Preserving civilian life is among the main goals of the Iraqi ground forces, Dorrian said. As the forces resume their march on Mosul, they are expected to liberate more than 1.5 million civilians who have long endured the hardline Islamist group’s rule.

The operation is expected to take several more weeks or potentially months, but military officials have expressed confidence the coalition will expel the Islamic State group from Mosul

“The Iraqis are quite capable of defeating [the Islamic State group]. They’ve already pushed them out of all these key areas around Mosul,” Dorrian said Friday. “This is a short pause, and they will continue the operation as they see fit.”

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