spect met with al Qaeda officials last year

Full Story 7: It was a stunt apparently designed to show how vulnerable Moscow and, in effect, other locations would be to a "dirty bomb."

But according to a U.N. report, Iraq tested a one-ton radiological bomb in 1987 but gave up on the idea because the radiation levels it generated were not deadly enough.

A "dirty bomb" uses nuclear material, such as spent fuel rods from nuclear reactors, to spread deadly radioactivity. Experts said they worry that determined terrorists could acquire the necessary supplies, which are poorly guarded or subject to few controls in some regions, according to the Council on Foreign Relations.