The key suspect in a plot to attack New York City with homemade bombs pleaded guilty in a federal court on Monday, Fox News has confirmed.

Najibullah Zazi, a 25-year-old former Denver airport shuttle driver, pleaded guilty to conspiracy to use weapons of mass destruction, conspiracy to commit murder in a foreign country and providing material support to Al Qaeda.

The Afghan native, who faces a life prison sentence without parole, told a federal judge Monday that he was trained by Al Qaeda for a "martyrdom" plan to attack the New York City subways.

He told prosecutors that he was armed with bomb-making components while en route to New York City last year, but flushed them down the toilet in a New York City apartment after getting spooked by a traffic stop on the George Washington Bridge while entering the city.

Zazi had driven a rented car from Denver to New York, arriving Sept. 10, 2009, the day before the eighth anniversary of the 2001 attacks.

He was allowed to go free after what was described as a routine traffic stop on the bridge, which connects New Jersey and New York. Authorities days later raided several Queens apartments, including a friend's home where Zazi had stayed.

The government alleges that the airport driver and others bought beauty supplies in Colorado to make peroxide-based bombs before he tried to mix the explosives in a hotel room there, before making the cross-country trip. Searches of Zazi's car after he arrived turned up bomb-making plans on a laptop computer, but no actual devices or materials.

The cooperation by Zazi suggests prosecutors hope to expand the case and bring charges against other suspects in his case and possibly other terrorism probes. At the time of Zazi's arrest, Attorney General Eric Holder called the case the most serious terrorism threat since the Sept. 11, 2001, attacks.

Amid the debate over whether alleged Al Qaeda and other terrorism suspects should be tried in civilian courts, federal prosecutors have sought to demonstrate that they can persuade suspects like Zazi to cooperate and provide more reliable information without coercion.

One of the people familiar with the Zazi case told the Associated Press that Zazi decided to offer the information after being warned that his mother could face criminal immigration charges.

Zazi's father was charged this month with trying to get rid of chemicals and other evidence. But it appears he was cut a break: After initially demanding that he be jailed in Brooklyn without bail, prosecutors agreed to a deal on Feb. 17 releasing him on $50,000 bond and allowing him to return to his home in suburban Denver.

By contrast, bond for a Queens imam charged with lying to the FBI about phone contact with Zazi when Zazi was in New York was set at $1.5 million. A friend of Zazi, New York cab driver Zarein Ahemdzay, was jailed without bail on a similar lying charge.

Another one of the people said that Zazi told prosecutors that he made roughly two pounds of a powerful and highly unstable explosive called triacetone triperoxide, or TATP.

Court documents indicate that Zazi and others bought acetone — nail polish remover — and other ingredients that can be used to make TATP. The same explosive was used by would-be shoe bomber Richard Reid in 2001 and the terrorists who carried out the London bombings in 2005 that killed 52 people.

In those instances, TATP was not the main charge; it was the detonator. The 1.5 grams in Reid's shoe was supposed to help detonate the plastic explosives aboard a jetliner, and it was used to set off a mixture of black pepper and hydrogen peroxide in London.

Experts have said the TATP in the Zazi case was probably going to be just the detonator.

The FBI's New York office and the U.S. attorney's office in Brooklyn declined to comment Monday.

Authorities say Ahmedzay and another New Yorker charged in the case, Adis Medunjanin, traveled to Pakistan with Zazi in 2008. Medunjanin has pleaded not guilty to charges he conspired to kill U.S. soldiers in Afghanistan and remains jailed.

The three men, former high school classmates in Queens, are scheduled to appear in federal court in Brooklyn on Feb. 25.

Officials earlier confirmed reports week that Zazi's uncle had been arraigned on a felony count in secret — a sign that he also could be cooperating.

LIVESHOTS: Zazi to Plead Guilty

The Associated Press contributed to this report.