WASHINGTON (Reuters) - The White house said on Tuesday that the Biden administration is still working to determine who is responsible for a rocket attack on U.S.-led forces in northern Iraq that killed a civilian contractor on Monday and injured a U.S. service member. Speaking at a White House briefing, press secretary Jen Psaki said we're still working through attribution with our Iraqi partners to determine precise attribution for this attack, she said, noting that the administration was outraged by it. (Reporting by Trevor Hunnicut and Alexandra Alper)