Zarein Ahmedzay, 25, pleaded guilty in federal court in Brooklyn to charges including conspiracy to use weapons of mass destruction in the foiled New York City subway bomb plot from fall 2009.
He said he, admitted plotter Najibullah Zazi and a third, unidentified man met with the leaders in Pakistan in 2008, where they offered to join the Taliban and fight U.S. forces in Afghanistan.
"They told us we would be more useful if we returned to New York City ... to conduct operations," he said. Asked by the judge what kind of operations, he responded, "Suicide-bombing operations."
He added: "I personally believed that conducting an operation in the United States would be the best way to end the war," he said.
as senior al Qaeda operatives Saleh al-Somali and Rashid Rauf, who were both killed in Pakistan. The U.S. Justice Department on Friday described al-Somali as the head of international operations for al Qaeda.
Al-Somali was killed in a drone strike in December. Rauf, a British militant linked to a jetliner bomb plot, was also killed in a predator strike in November 2008.
According to the government, Zazi and his co-conspirators were told by al Qaeda to "hit well-known structures and maximize the number of casualties," CBS News correspondent Bob Orr reports.
They agreed to carry out suicide attacks during the month of Ramadan (between August 22, 2009 and September 20, 2009) and Ahmedzay scouted unnamed potential targets in Manhattan, Orr reports.
Knox said Ahmedzay met with a third senior al Qaeda operative in a training camp in northern Waziristan in Pakistan. He has not been identified.
Prosecutors say Ahmedzay joined Zazi and another friend from their Queens high school on the trip to Pakistan to seek terrorism training.
Zazi, a Colorado airport van driver, admitted this year that he tested bomb-making materials in a Denver suburb before traveling by car to New York with the intent of attacking the subway system to avenge U.S. military involvement in Afghanistan.
Ahmedzay and the third suspect, Adis Medunjanin, had previously pleaded not guilty to charges they sought to join Zazi in what prosecutors described as three "coordinated suicide bombing attacks" on Manhattan subway lines. The bombings were planned for the days after the eighth anniversary of the Sept. 11, 2001, terror attacks, authorities said.
Officials have said a fourth suspect is in custody in Pakistan but have given no other details about him.
Ahmedzay - who had been licensed to drive a taxi in New York - said Friday they called off the operation once they discovered they were being watched by the FBI, and disposed of the explosive materials "at a location in Queens," he said.
He quoted heavily from the Quran during his plea and urged Americans to "stop supporting the war against Islam."
"I'm thankful for myself that I didn't harm anyone, but I feel someone else will do the same thing," he said.
Prosecutors say the attacks were modeled after the London transit system bombings in July 2005, when four suicide bombers killed 52 people and themselves in an attack on three subway trains and a bus.
The alleged New York plot was disrupted in early September when police officials stopped Zazi's car as it entered New York.
Last month, an Afghanistan-born imam linked to the suspects pleaded guilty to lying to the FBI when asked about the men. He was sentenced to time served and ordered to leave the United States.
Attorney General Eric Holder said Friday that the plot "makes clear we face a continued threat from al-Qaeda and its affiliates overseas."
"With three guilty pleas already and the investigation continuing, this prosecution underscores the importance of using every tool we have available to both disrupt plots against our nation and hold suspected terrorists accountable," he said.