Officials from the United States Central Command altered intelligence reports to portray a more optimistic picture of the war against the Islamic State in Iraq and Syria than events on the ground warranted, a congressional panel said in a report issued Thursday.

The interim report, from a task force established by the Republican chairmen of the House Armed Services Committee, Intelligence Committee and Defense Appropriations Subcommittee, found “widespread dissatisfaction” among Central Command intelligence analysts, who said superiors were doctoring their assessments of American efforts to defeat the Islamic State.