WASHINGTON (AP) — Militant groups in Afghanistan could still obtain U.S. government contracts and siphon off American taxpayer dollars because administrative flaws and misunderstandings are hampering a law aimed at weeding out corruption, a top auditor warned Thursday.

The special inspector general for Afghan reconstruction, John F. Sopko, said weaknesses mar procedures that the Defense Department tightened in 2012 to comply with a new federal law aimed at preventing militants from obtaining U.S. contract payments. Sopko said nearly $2 billion in government contracts was awarded in 2012, but he did not identify how much money was in jeopardy.