U.S. military officials are increasingly raising alarm about Iran’s role in Iraq. During a visit to Iraq, the nation’s new defense secretary, Leon Panetta, said Sunday that weapons supplied by Iran had become a “tremendous concern” for the United States. Panetta said, “This is not something we’re going to walk away from. It’s something we’re going to take on head on.” Panetta is in Iraq to discuss the possibility of keeping U.S. troops in Iraq beyond the scheduled pullout at the end of this year.