– Afghan troops traveling to the U.S. for training are going absent without leave at double the previous rate, raising security concerns in their homeland as well as in the U.S., according to a Pentagon watchdog.

The percentage of Afghan trainees in the U.S. going AWOL doubled last year to 13 percent from the historical average of 6 to 7 percent, the U.S. Special Inspector General for Afghanistan Reconstruction said in a report Friday. AWOL means the trainee is absent for more than 24 hours without proper permission.

Some of the missing trainees have never been tracked down and could pose a risk to the U.S., the report said.

"Given the deteriorating security situation in Afghanistan and the fact that Afghan trainees who violate the terms of their visas suffer virtually no consequences for going AWOL," the Defense Department said, the AWOL rate is "likely to either remain steady or increase."

Through July, Congress has appropriated $68.27 billion to the Pentagon to train and equip the Afghan National Defense and Security Forces, which sends personnel to the U.S. to gain expertise in areas such as aviation and counter-drug efforts. Nearly 16 years after U.S. troops first arrived in Afghanistan, the program is part of an effort to shift more responsibility for the country's security to local forces.

From August 2005 through March of this year, 253,977 foreign trainees arrived in the U.S. for training, 2,537 of them from Afghanistan. In that period, 320 foreign trainees went AWOL, with 152 of them being Afghan. Among the 152, 83 fled the U.S. or are unaccounted for.