US officials received intelligence that al-Qaida operatives had been 45 days from releasing a deadly gas into New York City subways when the plan was called off by Osama bin Laden's second-in-command in 2003, according to a book excerpt released Sunday on Time magazine's Web site. According to the investigative report by Pulitzer-prize winning journalist Ron Suskind, an informant close to al-Qaida management told US officials that Ayman al-Zawahri canceled the plan in January 2003, despite the likelihood that the strike would have killed as many people as the September 11 attacks. The informant said that operatives had planned to use a small, easily concealed delivery system to release hydrogen cyanide into multiple subway cars. US officials had already discovered plans for the device in the computer of a Bahraini jihadist arrested in February 2003, and they had been able to construct a working model from the plans. The easy-to-make device, called "the mubtakkar," meaning "invention" or "initiative," represented a breakthrough in weapons technology that "was the equivalent of splitting the atom," Suskind writes. All previous efforts to use the deadly gas, similar to that used in Holocaust-era gas chambers, in mass attacks had failed. The FBI declined to confirm the details of Suskind's account. Agency spokesman Bill Carter in Washington said Saturday that 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 Saturday. New York City Metropolitan Transportation Authority spokesman Tom Kelly declined comment. According to the report, US President George W. Bush was shown a model of the weapon in March 2003 and ordered alerts sent through the US 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 Time. The informant, who had become disgruntled with al-Qaida's leadership, linked the organization's top agent on the Arabian peninsula to the attacks, Suskind writes. The man was later killed in a violent standoff with Saudi authorities. The excerpt of Suskind's forthcoming book, "The One Percent Doctrine," was to appear in Monday's print edition of Time. Suskind is a former reporter for The Wall Street Journal.