The flow of new Islamic State recruits into Iraqi and Syria has slowed dramatically, reflecting a "fracturing in their morale," a top U.S. general in Baghdad said Tuesday.

The number of new recruits coming into the self-proclaimed caliphate has dropped from up to 2,000 per month to a new estimate of about 200 per month, said Air Force Maj. Gen. Peter Gersten, the deputy commander for operations for Operation Inherent Resolve, as the U.S. military mission in Iraq and Syria is known.

"When I first got here [one year ago], we were seeing somewhere between 1,500 and 2,000 foreign fighters entering the fight. Now that we've been fighting this enemy for a year, our estimates are down to around 200," Gersten told reporters at the Pentagon.

He also said U.S. intelligence estimates show an increase in the Islamic State militants' desertion rates, suggesting an erosion of overall combat power wielded by the group, which is also known as ISIS or ISIL.

Reports suggest the Islamic State group is facing severe financial problems and a cash shortage that has forced military commanders to slash basic pay for rank-and-file troops.

"We're seeing a fracture in their morale. We're seeing their inability to pay," Gersten said.

"We're seeing the inability to fight. We're watching them try to leave [ISIS]. In every single way, their morale is being broken. In every single way, their capability to wage war is broken," Gersten said.

In February, military officials said estimates for total Islamic State fighters in Iraq and Syria had dropped to between 19,000 and 25,000, down from prior figures ranging from 20,000 to more than 30,000, according to a defense official who spoke on condition of anonymity.

U.S. officials say it will likely require between eight and 12 Iraqi army brigades, or more than 30,000 soldiers, to successfully invade Mosul and retake it from the Islamic State group.