The top U.S. military commander in Iraq has told troops they must refrain from torturing or mistreating Iraqis.

Army General David Petraeus reminded American forces in an open letter dated Thursday they had to convince Iraqis that  "we - not our enemies - occupy the high moral ground."

General Petraeus was responding to a recent survey of U.S. ground troops in Iraq, which found more than one-third of all Marines and Army soldiers support torture if it leads to information about insurgents, or saves the lives of U.S. troops. Many also said they would not report a fellow serviceman for killing or injuring an Iraqi civilian.

The general says that while seeing a fellow trooper killed can lead to anger and a need for revenge, torture is "neither useful nor necessary."