The U.S. Defense Department said attacks on coalition forces by members of the Afghan military have left 45 soldiers dead so far this year.
U.S. Army Lt. Gen. James L. Terry, commander of the joint command at the International Security Assistance Force, said Afghan recruits would go through an eight-step vetting process that includes background checks and drug screening.
ISAF leaders, he added, were going through the records of attacks to get a better understanding of the threat factors.
"I would just say that what we all recognize is that this is society that's really been traumatized by 30-plus years of war," said Terry during a news briefing from Kabul. "It also has a gun culture."
Seth Jones, a scholar at the Rand Corp. and former U.S. adviser on Afghanistan, told National Public Radio the vetting process was a "huge, huge undertaking."
Jones added that it's difficult to determine if the growing number of green-on-blue attacks was on the rise "because training happened so quickly, or because the insurgency is making a much stronger, focused effort to infiltrate."