The Associated Press

LONDON — Homeland Security Secretary Michael Chertoff is downplaying the idea of a nuclear attack by terrorists after recent postings on al-Qaida-affiliated Web sites exhorted militants to pursue weapons of mass destruction for use against the U.S.

Chertoff, speaking at Oxford Union on Friday, said that while officials acknowledge al-Qaida's interest in developing such capability, the U.S. was more concerned about terrorists' use of conventional arms.

"The short answer is the intent is there. Its probability, particularly in the short term, is lower than conventional weapons," he said at Oxford's famed debating society.

Chertoff's remarks followed a series of anonymous postings on al-Qaida-affliated Web sites, including a 39-minute video, calling on militants to acquire weapons of mass destruction.

The Washington-based SITE Intelligence Group, which monitors militant Web traffic, said the video presents the U.S. as vulnerable and suggests that militants could use such weapons as a deterrent to any nuclear attack against an Islamic country.

Although none of the postings is known to be authentic, taken together they raise questions about whether jihadists have such capabilities and whether they can launch some kind of attack.

Copyright 2008 The Bismarck Tribune, a division of Lee Enterprises