WASHINGTON — Al Qaeda is declaring its intention to use biological, chemical, and nuclear weapons against American citizens.

In a story first reported by ABC News, an FBI spokesman, Richard Kolko said, “There have been several reports that al Qaeda will release a new message calling for the use of weapons of mass destruction (WMD) against civilians.”

ABC News also reported that the FBI has received no direct threat. But nonetheless, the bureau today sent a bulletin to 18,000 domestic law enforcement agencies.

The message, which ABC News reports is likely to be posted within 24 hours, would be Mr. bin Laden’s most explicit threat regarding weapons of mass destruction to date.

The new intelligence was gleaned by watching Al Qaeda’s network of private message boards and affiliated public sites, according to an intelligence official. Many analysts of Al Qaeda expect a videotape to be released, though the ability to monitor the feed of the video from Al Qaeda’s Pakistan-based al Sahab production studios was compromised in September. In the days prior to the fifth anniversary of the September 11, 2001 attacks, Mr. bin Laden’s first video appearance since 2004 was leaked to the American and Arabic media before Al Qaeda officially launched it to the wider internet.

The next message from Al Qaeda’s leader will mark a new emphasis on the kinds of weapons President Bush thought he’d find in Iraq. It is not however the first time Mr. bin Laden has spoken on the topic.

In October 2001, in an interview with Pakistan’s Dawn Newspaper, the master terrorist said, “I wish to declare that if America used chemical or nuclear weapons against us, then we may retort with chemical and nuclear weapons. We have the weapons as deterrent.”

Mr. bin laden has also sought an Islamic ruling on the matter from a Saudi Wahabi cleric who is currently in prison there, Sheik Nasser bin-Fahd. On May 21, 2003, Sheik Nasser issued an Islamic legal ruling or fatwa that gave Muslims the right to use nuclear weapons against America or its allies.

One American intelligence official who asked not to be identified explained the significance of the expected message as follows: “They have said they would kill millions of people before. Suleiman Abu Ghaith in 2002 said Al Qaeda had the right to kill millions of Americans. But this is getting into the ‘how.'”

The Commission on the Intelligence Capabilities of the United States Regarding Weapons of Mass Destruction in 2005 concluded that Al Qaeda maintained a crude capability to deliver a chemical weapons attack based on World War I era technology. It also said that Al Qaeda had programs to obtain nuclear and biological weapons.

The latest National Intelligence Estimate also concluded that Al Qaeda had rebuilt infrastructure it could use for WMD programs at its new base in the frontier tribal provinces of Pakistan. The former director of central intelligence, George Tenet, says in his memoir that an Al Qaeda military planner, Saif al Adel, attempted and failed to procure nuclear material while in Iran from former Russian scientists.