But Dr. Helen Caldicott, a pediatrician and president of the Nuclear Policy Research Institute, linked depleted uranium to higher rates of cancer and birth defects in Iraq following the Gulf War.

Depleted uranium ammunition is being used by U.S. troops in Iraq and could seriously harm civilians living there in the decades to come, said Caldicott, founding president of Physicians for Social Responsibility, an anti-nuclear group that shared the 1985 Nobel Peace Prize.

"We should be taking responsibility for what is happening over there," she told reporters at the National Press Club.

The Pentagon should test buildings in Iraq for depleted uranium, destroy ones with high levels and bury the material underground, Caldicott said.

The U.S. government also should compensate people with cancer related to the material, she said.

Depleted uranium is a byproduct of nuclear fuel production. It strengthens ammunition and gives weapons twice the range of ones using other heavy metals. Tanks made with depleted uranium have proven impenetrable by enemy weapons, the Pentagon said.

There has been controversy about it since its use during the Gulf War and the Balkans conflict, including some claims that European soldiers may have developed leukemia after being exposed to the material in Kosovo in 1999.

"We don't see anything from the science" indicating long-term health problems to people exposed to depleted uranium in the environment, said Dr. Michael Kilpatrick, the Defense Department's deputy director for deployment health support.

An ongoing study of 70 Gulf War veterans who were hit by weapons using depleted uranium in "friendly fire" incidents has found no major health problems for the soldiers or their 35 children, Kilpatrick said.

Kilpatrick said research on potential long-term impacts is continuing.

"We are looking at it scientifically. We are keeping an open mind to it," he said in an interview.