Washington, D.C. ? A report on deadly airstrikes in Afghanistan calls for better training for air and ground forces to reduce civilian casualties that have undermined the counterinsurgency campaign, The Associated Press has learned.

The recommendation on training and a second one urging a review of the use of air support are among a half-dozen findings in an unreleased report on a May 4 bombing that was aimed at Taliban militants but also killed dozens of Afghan civilians, two Defense Department officials said Wednesday. They spoke on condition of anonymity because the report has not been made public.

A separate recommendation is to review aircraft used for air support that troops call in to back them up, officials said.

The report says that U.S. air and ground forces headed to Afghanistan should receive advance training in the kinds of scenarios they could face, including situations that have resulted in civilian deaths, one official said. The report suggests periodic refresher training throughout troops’ tours of duty in the war zone, meaning that forces would get training early and often to reinforce battlefield tactics.