The activities of security contractors are "in conflict" with the US military's mission in Iraq, U.S. Secretary of Defense Robert Gates has said. But he acknowledged that the US could not manage without contractors, except by diverting thousands of troops, according to a report of BBC. On Thursday, three Iraqis were injured when guards from a UK company fired into a taxi in Kirkuk in northern Iraq. Security firms are under scrutiny after 17 Iraqis died in a clash involving guards from the US firm Blackwater. That incident, in September, led the Iraqi government to demand that the US sever all contacts with Blackwater. There have also been calls for the guards to be prosecuted in Iraq. Gates said: "As I see it, right now those missions are in conflict." "Just based on everything I've read and what our own team has reported, there have been instances where, to put it mildly, the Iraqis have been offended and not treated properly," he added.