A congressional panel Wednesday took up the uneasy topic of Afghan security forces turning on their international allies, incidents that have fueled mutual distrust at a critical juncture of the long-running conflict.

Rep. Buck McKeon, the California Republican who chairs the Armed Services Committee, said that existing security procedures failed to identify 42 attackers between 2007 and 2011; 39 of those attacks were by members of the Afghan National Security Force and three by contracted employees.

"This is 42 attacks too many, and the new process must do better," McKeon said.

That number did not include the latest incident, in which a man wearing an Afghan National Army uniform killed a coalition forces member in southern Afghanistan on Tuesday.

The panel heard testimony from four defense officials who laid out delicate issues pertaining to Afghan security forces, among them the vetting of Afghans brought onto coalition bases to provide security.

The defense officials said that in 58% of cases, the attackers were not puppets of insurgent groups but acted on their own accord, perhaps over a personal dispute.

Such disputes can arise from cultural misunderstanding, religious and ideological friction or combat stress, said Brig. Gen. Stephen Townsend, director of the Pakistan/Afghanistan Coordination Cell in the Joint Chiefs of Staff office.

He said cultural training has been vital for U.S. soldiers and now, the Afghans are considering doing the same in providing better understanding of Americans.