The watchdog for US spending in Afghanistan says lax accountability in a $1.1 billion program supplying fuel to the Afghan National Army needs "immediate attention" before control of the program is turned over to the Kabul government in less than four months.

There is no proof the fuel is actually being used by Afghan security forces for their missions, meaning it's not known how much fuel has been lost, stolen or diverted to the insurgency, according to a report released Monday by Special Inspector General for Iraq Reconstruction John F. Sopko.

The report is the latest bad news surrounding a key element of the US exit strategy for Afghanistan. Washington has spent billions of dollars on the international coalition's effort to train and equip Afghan forces it hopes eventually will be able to fight the Taliban on their own.