KAMPALA, Uganda — A series of defections have left a brutal warlord struggling to stay in charge of his Central African rebel group, a U.S.-based watchdog group said in a report Wednesday, raising hopes the Lord's Resistance Army is possibly weaker than ever.

The fugitive warlord Joseph Kony, who is wanted by the International Criminal Court for war crimes and crimes against humanity, is losing his grip on the rebel group that originated in Uganda but which now is active in Congo and Central African Republic, the Resolve LRA Crisis Initiative said.

About 15 percent of Kony's fighters have defected since January 2012, forcing the warlord to start executing disobedient or disloyal commanders amid a "transition of power to younger Ugandan officers."

"This upheaval, combined with the awareness that Kony and senior officers have of the declining will to fight in the ranks, likely makes senior officers suspicious, and even paranoid, of each other," the report said. "Come Home messages addressing these dynamics and targeting specific commanders could exploit these tensions in order to weaken the LRA."

Some 100 U.S. military advisers are helping about 3,000 African troops in a military mission that encourages defections from the LRA through "Come Home" messages distributed in the bush. Helicopter-mounted speakers spread this message and leaflets are scattered in the jungle, tactics that apparently seem to be working with a group whose fighters are highly mobile. The report cited the accounts of LRA defectors who say more rebels would risk defecting if they were assured of help in reintegrating back into their original villages.

But the lack of reliable intelligence on LRA commanders — and where exactly they are hiding — limits the effectiveness of the messages, the report said.

Kony, who has eluded capture for more than two decades despite millions of dollars spent to hunt him down, is now hiding in territory controlled by Sudan's military, according to the report. He is in Kafia Kingi, a disputed area along the Sudan-South Sudan border where African Union troops tasked with catching Kony don't have access. Watchdog groups said they are concerned that Kony can retreat there whenever his pursuers get close.

Although Sudan consistently denies supporting Kony or harboring him and his commanders, Ugandan military officials and some watchdog groups say he benefits from Sudanese military support.

Kony's rebel group is vastly diminished from previous years, and its forces now don't exceed 500, a figure also cited by Brig. Dick Olum, a Ugandan military official who previously led African troops on the anti-Kony African Union mission. Some of Kony's top lieutenants have recently been captured or killed in combat, and last year an LRA commander believed to be Kony's military strategist was seized by Ugandan troops.

The LRA, which originated in Uganda in the 1980s as a popular tribal uprising against the government, has become notorious for recruiting children as fighters and forcing girls to be sex slaves. Military pressure forced the LRA out of Uganda in 2005, and the rebels scattered across parts of central Africa.

The mission suffered a setback earlier this year after rebels deposed a president in Central African Republic and asked all foreign troops operating in the country to leave. Active military operations against Kony have since been suspended there.