Al-Qaeda was ready to launch a chemical weapons attack on the New York City subway system in 2003 but it was called off by Osama bin Laden’s deputy for unknown reasons.

Al-Qaeda terrorists came within 45 days of attacking the New York subway system with a lethal gas similar to that used in Nazi death camps. They were stopped not by any intelligence breakthrough, but by an order from Osama bin Laden’s deputy, Ayman Zawahiri. And the U.S. learned of the plot from a CIA mole inside al-Qaeda. These are some of the more startling revelations by Pulitzer Prize-winning author Ron Suskind, whose new book The One Percent Doctrine is excerpted in the forthcoming issue of TIME.

Several commenters, including John Little, are understandably confused as to why the attack–using what TIME dubs the “holy grail of terror R&D” –was called off and hasn’t been reinstated. (I would insert a Pancho and Lefty reference here but have already used my quota for the week.) I believe C.S. Scott is right, though, that the news of a “CIA mole inside al-Qaeda” is actually even bigger news.

Patrick Frey is just glad that TIME published this rather than al Qaeda favorite Newsweek. Alas, they’re on the trail, too.

UPDATE: The excerpt is here.

One of the jihadists, Bassam Bokhowa, an educated fiftyish professional, with computer skills, had visited an apartment in Saudi Arabia. And there, a joint Saudi-U.S. counterterrorist unit, formed after the meeting with Bandar in his study, found a computer. The contents were dumped onto a separate hard drive, which was sent to the United States for imaging—a way to suck out digitalia, encrypted or not.

That’s where they found it: plans for construction of a device called a mubtakkar. It is a fearful thing, and quite real.

Precisely, the mubtakkar is a delivery system for a widely available combination of chemicals—sodium cyanide, which is used as rat poison and metal cleanser, and hydrogen, which is everywhere. The combination of the two creates hydrogen cyanide, a colorless, highly volatile liquid that is soluble and stable in water. It has a faint odor, like peach kernels or bitter almonds. When it is turned into gas and inhaled, it is lethal. For years, figuring out how to deliver this combination of chemicals as a gas has been something of a holy grail for terrorists.

Ramzi Yousef plotted to release the gas into the ventilation system of the World Trade Center prior to bombing the place in 1993 and couldn’t quite manage it. The famous chemical attack by the doomsday cult Aum Shinrikyo on the Tokyo subway in March 1995—the release of sarin gas that killed 12 people and sent about 5,000 to area hospitals—was followed, two months later, by an attempted cyanide gas attack by cult members. A small fire, set in a Tokyo restroom that ventilated onto a subway platform, was designed to disperse the gas and was extinguished by alert subway guards.

Terrorism experts inside many governments have been on the lookout for reports of a solution to these engineering hurdles. Now, the CIA had found it. Mubtakkar means “invention” in Arabic, “the initiative” in Farsi. The device is a bit of both. It’s a canister with two interior containers: sodium cyanide is in one; a hydrogen product, like hydrochloric acid, in the other; and a fuse breaks the seal between them. The fuse can be activated remotely—as bombs are triggered by cell phones—breaking the seal, creating the gas, which is then released. Hydrogen cyanide gas is a blood agent, which means it poisons cells by preventing them from being able to utilize oxygen carried in the blood. Exposure leads to dizziness, nausea, weakness, loss of consciousness and convulsions. Breathing stops and death follows. (Since blood agents are carried through the respiratory system, a gas mask is the only protection needed. If one is exposed to blood agents, amyl nitrite provides an antidote, if administered quickly enough.)

In a confined environment, such as an office building’s ventilation system or a subway car, hydrogen cyanide would cause many deaths. The most chilling illustration of what happens in a closed space comes from a 20th century monstrosity. The Nazis used a form of hydrogen cyanide called Zyklon B in the gas chambers of their concentration camps.

When the plans were discovered on Bokhowa’s hard drive, Rolf Mowatt-Larssen, the cia’s operational chief for wmd and terrorism, and his counterpart, “Leon,” who heads the analytical side of that same division, went into something just shy of a panic. Leon instantly pulled together a team to make a model of the device that he could eventually test.

It’s interesting and, as AllahPundit notes, rather chilly. Still, I can’t help being a bit dubious of this level of detailed intelligence being in the hands of a reporter, kept secret long enough for him to write a book, combined with the lack of an attack in the subsequent three years.

Oh–and this doesn’t make TIME’s cover. . . .

UPDATE: AP adds credence to the account and simultaneously downplays it:

The FBI declined to confirm the details of Suskind’s account. Spokesman Bill Carter in Washington said Saturday the bureau would have no comment on the excerpted material. A New York Police Department spokesman said authorities had known of the planned attack. “We were aware of the plot and took appropriate precaution,” Paul Browne said. New York City Metropolitan Transportation Authority spokesman Tom Kelly declined comment.

According to the report, President Bush was shown a model of the weapon in March 2003 and ordered alerts sent through the U.S. government. When intelligence arrived that al-Zawahri had called off the attack, Bush worried that something worse was in the works, Suskind writes. At least two of Suskind’s sources remembered Bush saying, “This is bad enough. What does calling this off say about what else they’re planning? … What could be the bigger operation Zawahri didn’t want to mess up?” the author said. “What has been concluded for the most part is this: al-Qaida’s thinking is that a second-wave attack should be more destructive and more disruptive than 9/11,” Suskind told the magazine in an interview. [emphasis added]

The informant, who had become disgruntled with al-Qaida’s leadership, linked the organization’s top operative on the Arabian peninsula to the plot, Suskind writes. The operative was later killed in a standoff with Saudi authorities.

Interesting. There was a tightening of security at Penn Station last October but it turned out to be a false alarm–a soda can. I don’t recall any news from 2003 on a similar event and can’t find any via a quick Google search.