The man, whom Ashcroft said was an al Qaeda operative, was captured May 8th as he flew into Chicago’s O’Hare International Airport from Pakistan, CNN reported. Ashcroft said the suspect was being transferred from Justice Department custody to the Defence Department after officials determined he was an “enemy combatant” who posed a serious and continuing threat to US citizens.

A “dirty bomb” is a conventional bomb equipped with radioactive material designed to spread over a wide area.

Ashcroft made the announcement in Moscow, where he is meeting with Russian officials to discuss the war on terrorism.

In May this year, Russian nuclear energy minister Aleksandr Rumyantsev toured the United States and reached agreement with his American counterpart Spencer Abraham on “dirty bombs”. The agreement was to create a US-Russia task force to look at better safeguarding low-grade radioactive materials that could be used to fashion a “dirty bomb” — which does not have a nuclear chain reaction but can disperse radiation over a limited area by using conventional explosives.

These non-weapon radiation sources — isotopes used in medicine, construction and, often in Russia, as a power source in remote locations — are “potentially attractive targets for theft” and could be used by terrorists to make a dirty bomb, Abraham said.

Rumyantsev said his government has acted to improve the protection of such radioactive materials. As an example, he cited a recent decision to let Minatom control the disposition of radioactive material used in beacons used for directional lights in remote parts of Russia. According to a Russian government report recently cited in the Washington Post, many of these beacons have not been visited by government staff for years and have fallen prey to scrap metal thieves and the elements.

Minatom’s new efforts to control the disposition of these devices “shows how serious this issue is and that we’re ready to solve it,” Rumyantsev said.

The United States has similar problems. The Nuclear Regulatory Commission acknowledged that about 1,500 such radiation devices have disappeared across the United States over the past five years and that about half are missing.

Ashcroft’s announcement in Moscow was apparently aimed to get a better Moscow’s focus on the “dirty bomb” issue.