by USA Today's Jim Michaels

Iraqi security forces in Mosul are closing in on an increasingly desperate and shrinking band of Islamic State fighters who are using human shields to try and slow the U.S.-supported offensive, a top U.S. commander said Wednesday.

“There’s no limit to their exploitation of the people,” Army Maj. Gen. Joseph Martin told USA TODAY in an interview from Baghdad.

Worn down by airstrikes and months of ground attacks, the Islamic State, also known as ISIS, can no longer conduct effective assaults to defend its positions inside Iraq’s second-largest city. 

The ISIS force has shrunk as militants are killed, and its weapons are limited to small arms, grenades and some improvised explosives, Martin said.

Earlier this year the Pentagon estimated that fewer than 2,000 militants were in Mosul, but Iraq's military says the enemy force has been reduced to a few hundred.

Iraqi Prime Minister Haider al-Abadi said this week that victory against ISIS will be announced in a “very short time.”

When the offensive began in October, Iraqi forces faced a sophisticated enemy that used drones for surveillance and manufactured its own weapons and ammunition. It was able to conduct coordinated attacks.

“They were a formidable military that has been brought to its knees,” Martin said.

Militants have shot people trying to escape and blown up buildings with civilians trapped inside. The United Nations reported this month an increase in the number of civilians killed by ISIS as residents tried to flee the city.

In a June 1 incident, militants shot and killed at least 163 fleeing civilians, including women and children, near a soft drink factory, the U.N. said. 

Up to 150,000 civilians remain trapped in Mosul and face a shortage of food and clean water, the U.N. said.

The remnants of ISIS are holed up in a few neighborhoods in the Old City in western Mosul, an area with narrow streets and ancient buildings.

The presence of thousands of civilians in densely packed neighborhoods has forced Iraq’s ground forces to pick their way through the parts of the city still controlled by ISIS to avoid civilian casualties.

Earlier this week, ISIS fighters attempted a counterattack to break through the Iraqi cordon and escape. Martin said the counterattack was crushed by Iraq’s military.

“They’re trapped and they’re desperate,” Martin said. “They’ve got two choices right now: surrender or die.”

The defeat of ISIS in Mosul would be a significant loss for the militants, which swept into the city three years ago as Iraq’s military collapsed in the face of the onslaught.

ISIS leader Abu Bakr al-Baghdadi declared the establishment of a caliphate from Mosul in 2014 after the terrorist group captured the city.

Last week militants destroyed the historic al-Nuri mosque where al-Baghdadi made the speech as Iraqi forces advanced on the site.

The U.S. military has deployed more than 5,000 troops in Iraq to support the training and assistance mission. The Iraqi forces are backed by coalition airstrikes.

The coalition support appears to be working. Iraq’s security forces have continued to advance in Mosul despite high casualties as the Iraqi forces engage militants in difficult street fighting.

“What we’re seeing in Mosul right now is grit,” Martin said.