US government security agents will begin accompanying private armed guards that protect US diplomatic convoys after a bitterly disputed shootout in which Iraqi civilians were killed, the US State Department said Friday. The announcement marked the first US steps to tighten supervision of companies like Blackwater USA, which Iraqi officials accuse of unprovoked killings in the September 16 firefight in Baghdad. State Department spokesman Sean McCormack said the measures were based on a preliminary report by US investigators in Iraq, but he did not immediately reveal the findings. Secretary of State Condoleezza Rice ordered that the department's own security agents begin accompanying Blackwater guards, and additional agents are en route to Baghdad, McCormack said.