A British analyst argues that security weaknesses in Pakistan could allow al-Qaeda or Taliban extremists to seize a nuclear weapon.

If it were in a position to do so, Al Qaeda would use Pakistan's nuclear weapons in its fight against the United States, a top leader of the group said in remarks aired on Sunday.

Michael Krepon, a longtime expert on nuclear threat reduction, is questioning a finding released this week asserting the likelihood that a weapon of mass destruction will be used somewhere around the globe within the next five years.

Seven years after the 2001 anthrax attacks, a congressionally ordered study finds a growing threat of biological terrorism and calls for aggressive defenses on par with those used to prevent a terrorist nuclear detonation. Due for release next week, a draft of the study warns that future bioterrorists may use new technology to make synthetic versions of killers such as Ebola, or genetically modified germs designed to resist ordinary vaccines and antibiotics.

Brian Michael Jenkins, a longtime terrorism expert with the RAND Corporation, says in this interview that the threat of nuclear terrorism lies more in the realms of Hollywood dramas and terrorist dreams than in reality. He argues that political leaders should not exaggerate the dangers of nuclear terrorism as the fear this creates plays into the terrorist strategy.

Officials at the Department of Homeland Security have overstated the performance of costly new radiation detectors designed to prevent the importation of radiological materials that could be used in bombs, according to an unreleased government report.

The international community must agree on a common set of security standards to ensure that plans to expand the use of nuclear power do not increase opportunities for terrorists or rogue nations to acquire sensitive materials, according to Thomas D’Agostino, head of the National Nuclear Security Administration.

Top federal officials and medical experts gathered in Washington on Thursday to consider this nightmare vision. Their conclusion: Cities and states are frightfully ill-prepared for dealing with an attack using a small nuclear bomb.

An evolving U.S. national policy aims to create a system of nuclear forensics, in which scientific analysis could quickly identify the source of a nuclear attack or attempted attack.

A nuclear device assembled by terrorists is likely to have a "relatively low yield," much smaller than the 10-kiloton weapon dropped on Hiroshima at the end of World War II, according to the chief nuclear scientist with the U.S. Homeland Security Department. Nevertheless, even a small nuclear explosion would probably be viewed as a "success" by any nonstate actor.