Defense Secretary Donald Rumsfeld says Americans will not accept dishonorable behavior, vowing again that those responsible for the prisoner abuse scandal in Iraq will be punished.

Mr. Rumsfeld did not appear bothered by new published charges that he personally authorized the harsh treatment of Iraqi detainees, as he spoke Monday at the conservative Heritage Foundation in Washington. It was his first public address since his surprise, lightning visit to Baghdad last week.

During that trip, Mr. Rumsfeld toured the notorious Abu Ghraib prison, where a small group of U.S. soldiers is accused of abusing Iraqi detainees, including acts of sexual humiliation.

But since then, new published reports have emerged alleging senior officials may also have been involved. The "New Yorker" magazine, for example, claimed Mr. Rumsfeld approved the use of sexual humiliation and physical coercion in prisoner interrogations.

An aide to the Defense Secretary has dismissed that claim and Mr. Rumsfeld did not mention it in his Heritage Foundation address. Instead, Mr. Rumsfeld again called the scandal a body blow and insisted top Pentagon leaders were appalled by the now highly-publicized abuse photos. "As we saw some of those pictures in the Pentagon and looked at each other's faces, you could feel the shock that we felt and disappointment that some in our country's uniform could sully by that behavior," he said.

Mr. Rumsfeld went on to say those responsible will be held accountable. He said the scandal was uncovered by the military and revealed by the military, providing an important lesson. "The world will see that Americans will not accept dishonorable behavior," he said.

Other new articles, in the New York Times newspaper and Newsweek magazine, claim so-called "high-value" detainees like ousted Iraqi leader Saddam Hussein have also faced harsh treatment.

But in Baghdad, U.S. military spokesman, Brigadier General Mark Kimmitt, denied that was the case. "All our investigations at this point have indicated that there was no abuse, no harassment conducted with the high-value detainees," he said.

General Kimmitt also revealed Monday that U.S. forces have for the first time discovered an artillery shell containing the deadly nerve agent, Sarin.

But in Washington, top officials including Mr. Rumsfeld urged caution, noting field tests are often not perfect. "What we ought to do is to get the samples some place where they can be tested very carefully before coming to a conclusion as to precisely what it was," he said.

If confirmed, the discovery would mark the first time a significant weapon of mass destruction has been found since the Iraq war began last year, a war largely launched because of the alleged existence of such weapons.

The shell found in recent days in Baghdad had actually been rigged as an improvised explosive device like those routinely planted to kill coalition troops. It detonated but dispersed only a tiny amount of nerve gas.