In a secret operation, the United States last month removed from Iraq nearly two tons of uranium (search) and hundreds of highly radioactive items that could have been used in a so-called dirty bomb (search), the Energy Department disclosed Tuesday.

The nuclear material was secured from Iraq's former nuclear research facility and airlifted out of the country to an undisclosed Energy Department laboratory for further analysis, the department said in a statement.

Energy Secretary Spencer Abraham (search) described the previously undisclosed operation, which was concluded June 23, as "a major achievement" in an attempt to "keep potentially dangerous nuclear material out of the hands of terrorists."

The haul included a "huge range" of radioactive items used for medical and industrial purposes, said Bryan Wilkes, a spokesman for the Energy Department's National Nuclear Security Administration.

Much of the material "was in powdered form, which is easily dispersed," said Wilkes.

The statement provided only scant details about the material taken from Iraq, but said it included "roughly 1,000 highly radioactive sources" that "could potentially be used in a radiological dispersal device," or dirty bomb.

Also ferried out of Iraq was 1.95 tons of low-enriched uranium, the department said.

Wilkes said "a huge range of different isotopes" were secured in the joint Energy Department and Defense Department operation. They had been used in Iraq for a range of medical and industrial purposes, such as testing oil wells and pipelines.

Uranium is not suitable for making a dirty bomb. But some of the other radioactive material — including cesium-137, colbalt-60 and strontium — could have been valuable to a terrorist seeking to fashion a terror weapon.

Such a device would not trigger a nuclear explosion, but would use conventional explosives to spread radioactive debris. While few people would probably be killed or seriously affected by the radiation, such an explosion could cause panic, make a section of a city uninhabitable for some time and require cumbersome and expensive cleanup.

Nuclear nonproliferation (search) advocates said securing radioactive material is important all over the world.

A recent study by researchers at the Center for Nonproliferation Studies at the Monterey Institute of International Studies concluded it is "all but certain" that some kind of dirty bomb will be set off by a terrorist group in the years ahead. There are just too many radioactive sources available across the globe, the report said.

"This is something we should be doing not just in Iraq," Ivan Oelrich, a physicist at the Federation of American Scientists, said when asked to comment on the Energy Department announcement.

Oelrich hesitated to characterize the threat posed by the uranium and other radioactive material secured in the secret U.S. operation because few details were provided about the material. The Energy Department refused to say where the material was shipped.

But Oelrich said it is widely believed that medical and industrial isotopes can be used in a dirty bomb.

The low-enriched uranium taken from Iraq, if it is of the 3 percent to 5 percent level of enrichment common in fuel for commercial power reactors, could have been of value to a country developing enrichment technology.

"It speeds up the process," Oelrich said, adding that 1.95 tons of low-enriched uranium could be used to produce enough highly enriched uranium to make a single nuclear bomb.