The U.S. military says airstrikes over the past week have killed about 350 Islamic State fighters in the Iraqi city of Ramadi — and that may have reduced by half the number of fighters defending the city.

IS took Ramadi seven months ago.

Col. Steve Warren, a spokesman for the U.S. military in Baghdad, tells reporters at the Pentagon that despite these losses, IS defenders still hold much of central Ramadi.

Warren says Iraqi government forces are advancing slowly because they face booby traps and mines.

Separately, Defense Secretary Ash Carter says Iraqi progress in retaking Ramadi has been "disappointingly slow." He's declining to predict how long the fight will last, but says he has no doubt Ramadi will fall.