A flag belonging to the Islamic State fighters is seen on a motorbike after forces loyal to Syria's President Bashar al-Assad recaptured the historic city of Palmyra, in Homs Governorate in this handout picture provided by SANA on March 27, 2016. REUTERS/SANA/Handout via Reuters

WASHINGTON (Reuters) - The number of foreign fighters joining the Islamic State militant group in Iraq and Syria has decreased sharply in the past year to about 200 a month, a U.S. military official said on Tuesday.

That is a drastic decline from about a year ago when between 1,500 and 2,000 foreign fighters were joining the group in Iraq and Syria each month, said Air Force Major General Peter Gersten, deputy commander for operations and intelligence for the U.S.-led coalition, during a news briefing.

Earlier this month, the State Department said the number of Islamic State fighters in Iraq and Syria was lower than at any time in the past two years.

Syria has become the main global incubator for a new generation of militants as Islamic State recruited as many 31,000 foreign fighters in the past 18 months, according to a report published by a former British spy chief last year.

Gersten added that the number of fighters defecting from Islamic State was increasing as well, but he did not give a specific number.

“We’re seeing a fracture in their morale, we’re seeing their inability to pay, we’re seeing the inability to fight, we’re watching them try to leave Daesh in every single way,” Gersten said, using an Arabic acronym for Islamic State.