Sen. John McCain (search) said Sunday that abuse of Iraqi prisoners by U.S. soldiers, alleged anew in a report and under investigation again by the Army, are hurting the nation's image abroad.

"We've got to have it stopped," McCain, R-Ariz., said on "This Week" on ABC. "I don't know if these allegations are true or not, but they have to be investigated."

Human Rights Watch issued a report Friday based on interviews with a captain and two sergeants who served in a battalion of the 82nd Airborne Division (search) stationed at a military base near Fallujah. The report alleged that Army soldiers systematically tortured Iraqi detainees from 2003 into 2004, hitting them with baseball bats and dousing them with chemicals.

The Army says it has opened an investigation into a soldier's allegations that he witnessed and heard about widespread prisoner abuse, including torture and a beating with a baseball bat, while serving at a base in Iraq.

McCain acknowledged that the captain in the Human Rights Watch report had contacted his staff, which McCain said was conducting its own investigation.

McCain, who was held prisoner during the Vietnam War, has proposed an amendment to the defense bill to make interrogation techniques outlined in the Army field manual standard for treatment of all detainees in the Defense Department's custody. Another change he has proposed would expressly prohibit cruel, inhumane and degrading treatment of those in U.S. custody no matter where they are held.

"We've got to make it clear to the world that American doesn't do it. It's not about prisoners. It's about us," he said.