Iraqi forces will resume their push against Islamic State inside Mosul in the coming days, a U.S. battlefield commander said, in a new phase of the two-month-old operation that will see American troops deployed closer to the front line in the city.

The battle for Mosul, involving 100,000 Iraqi troops, members of the Kurdish security forces and Shi’ite militiamen, is the biggest ground operation in Iraq since the U.S.-led invasion of 2003. The upcoming phase appears likely to give American troops their biggest combat role since they fulfilled President Barack Obama’s pledge to withdraw from Iraq in 2011.

Elite Iraqi soldiers have retaken a quarter of Mosul, the jihadists’ last major stronghold in Iraq, but their advance has been slow and punishing. They entered a planned “operational refit” this month, the first significant pause of the campaign.

A heavily armoured unit of several thousand federal police was redeployed from the southern outskirts two weeks ago to reinforce the eastern front after army units advised by the Americans suffered heavy losses in an Islamic State counter-attack.