A key associate of admitted al Qaeda terrorism suspect Najibullah Zazi pleaded guilty on Friday at the U.S. District Court in Brooklyn, as prosecutors alleged the men accused of an attempted bombing of the New York City subway were in contact with a top al Qaeda leader involved in an averted 2006 plot to bomb airlines over the Atlantic Ocean.
Zarein Ahmedzay, 25, pleaded guilty to three charges tied to his role in a plot to target the New York City subway system. He pleaded guilty to conspiracy to use a weapon of mass of destruction, conspiracy to commit murder in a foreign country and providing material support to al Qaeda.
According to officials involved with case, Zazi, Ahmedzay and another suspect were in contact with senior members of al Qaeda on an August 2008 trip to Pakistan.
Zazi, who was arrested in Denver in September 2009, has been cooperating with the federal government and pleaded guilty in February, admitting he planned to attack the New York subways close to the eighth anniversary of Sept. 11.
Prosecutors claimed today that Ahmedzay, Zazi and a third suspect told the top tiers of al Qaeda that they wanted to fight against U.S. soldiers in Afghanistan, but were convinced to return to the United States to carry out attacks.
Zazi has said he was recruited by al Qaeda in Pakistan when he traveled there intending to join the Taliban.
Zazi and Ahmedzay allegedly traveled overseas to Pakistan with Adis Medunjanin, who also lived in the New York area. Medunjanin was charged for his alleged role in the plot in late February, but has pleaded not guilty.
According to information presented at Friday's hearing, the men were in contact with Saleh al-Somali, the former head of international operations for al Qaeda, and Rashid Rauf, one of al Qaeda's top lieutenants who was involved in helping plan the thwarted 2006 trans-Atlantic liquids aviation plot.
That plot was intended to strike at least seven jetliners bound for North America on United Airlines, American Airlines and Air Canada flights into New York, Washington, Chicago, San Francisco, Montreal and Toronto. The plotters intended to smuggle explosive liquid peroxide colored with dye inside sport drink bottles, and to assemble the bombs on the aircraft.
According to counterterrorism officials, Rauf, a British citizen, put the alleged U.K. plotters in touch with members of al Qaeda. The averted attack led to restrictions being placed on liquids for air travel.
Both Rauf and al-Somali have been killed in U.S.-coordinated anti-terrorism operations. Rauf is believed to have been killed in a drone attack in late 2008. Al-Somali was killed in December 2009 in another drone strike in Pakistan's tribal region.
Al-Somali was heavily involved in al Qaeda's propaganda efforts and is believed to have been working with western al Qaeda recruits upon their arrival into the tribal of areas of Pakistan.
Contacted by ABC News, former Department of Homeland Security Secretary Michael Chertoff said in an interview, "This case shows the effort by al Qaeda in the frontier area to recruit and launch Westerners against Western targets."
Chertoff served as DHS secretary during the time of the 2006 aviation plot and oversaw the U.S. security response.
Asked about his impressions of the claim that Zazi was in contact with an al Qaeda facilitator of the liquid explosives plot, Chertoff said, "What is concerning is the ability to recruit people who are legitimate U.S. citizens or residents and turn them. That has always been the real fear that we have faced over the past few years. We've begun to see that we've had some success in doing it although certainly not as much as they've had in Western Europe."
Zazi, who worked as an airport shuttle bus driver in Denver, was arrested after more than a year of surveillance by the FBI. He was caught with chemicals and hydrogen peroxide-based beauty products to make peroxide bombs, according to court documents filed in the case.
Zazi's father was indicted on Feb. 1 on charges that he helped conceal objects that Zazi was using in his bomb-making attempts.
During Friday's plea hearing, Ahmedzay, a New York City cab driver, admitted that he was involved in selecting the targets for subway bombings that allegedly were to have taken place within days after Sept. 11, 2009.
According to FBI officials, Zazi told agents interviewing him that he and his co-conspirators would try to bomb the 1, 2, 3 and 6 New York subway lines at rush hour.
"The facts disclosed today add chilling details to what we know was a deadly plot hatched by al Qaeda leaders overseas to kill scores of Americans in the New York City subway system in September 2009," Attorney General Eric Holder said in a statement released on Friday. During the hearing Ahmedzay said, "I'm thankful I did not do anything to harm anyone but I feel someone else might."
He also launched into anti-Semitic comments and made statements about the U.S. wars overseas in Iraq and Afghanistan.
Sentencing for Ahmedzay has been set for July, 30, 2010. Zazi is due to be sentenced in June.
ABC News' Luis Martinez contributed to this report.