New York (CNN) -- A New York taxi driver pleaded guilty Friday to involvement in a plot to blow up crowded subway trains.

After entering his plea Zarein Ahmedzay delivered a message: "I strongly urge the American people to stop supporting the war against Islam," he said, adding, "I am thankful for myself that I did not do anything to harm anyone but fear someone else will do the same thing."

Prosecutors said Ahmedzay and another man, Adis Medunjanin, conspired with Najibullah Zazi on the attack in mid-September 2009, which authorities thwarted.

Zazi pleaded guilty and has been cooperating with authorities, investigators have said. Medunjanin has pleaded not guilty.

During Ahmedzay's hearing, prosecutors for the first time revealed the names of the two al Qaeda leaders who, officials said, ordered the plot: Saleh al-Somali, head of international operations for al Qaeda, and Rashid Rauf, a key operative.

U.S. officials said both al Qaeda figures were killed in drone in attacks in Waziristan, the tribal region along the border between Pakistan and Afghanistan. Rauf was reported killed in a drone attack in Waziristan in November 2008; al-Somali was reported killed in December 2009, U.S. officials said.

U.S. Attorney General Eric Holder, in a written statement, said the facts disclosed Friday "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. This plot, as well as others we have encountered, makes clear we face a continued threat from al Qaeda and its affiliates overseas."

"Prosecution underscores the importance of using every tool we have available to both disrupt plots against our nation and hold suspected terrorists accountable," Holder said.

Ahmedzay previously pleaded not guilty to making false statements to the FBI about the plot.

But Friday, appearing before before Chief U.S. Magistrate Judge Steven M. Gold in U.S. District Court, he pleaded guilty to conspiracy to use a weapon of mass of destruction against people in the United States; conspiracy to commit murder; and providing material support to a foreign terrorist organization.

Ahmedzay told the court that he, Zazi and a third man traveled to Pakistan in August 2008 to join jihadists fighting in Afghanistan, but they were turned away. But al Qaeda leaders in Pakistan told the group they would be more helpful to the jihad cause if they conducted suicide attacks in New York.

"We discussed the matter amongst ourselves, and we agreed to go forward with the plan," he said. "I personally believed that conducting an operation in the United States would be the best way to end the wars."

At one point, Ahmedzay said, he began to have second thoughts but ultimately committed to the plan. He said his primary input was to develop targets because he was a taxi driver and knew the city well. Eventually, the three settled on an attack on subway trains during the month of Ramadan, but abandoned that plan when they believed law enforcement was watching them.

Ahmedzay concluded his statement to the court with his belief that "Zionist Jews" are "the real enemies of this country" who are "destroying this country from within" and "want a permanent shadow government within the government of the United States."

He faces a sentence of up to life in prison. He is scheduled to be sentenced at the end of July.

"Ahmedzay's plea makes clear that he betrayed his adopted country and its people by providing support to al Qaeda and planning to bring deadly violence to New York," said FBI Director Robert S. Mueller in a written statement.

Robert Gottlieb, attorney for Medunjanin, said Friday's developments do not change his client's plans to proceed to trial. "The evidence and the facts as they pertain to him will come out in court," Gottlieb said.

No trial date has been set for Medunjanin.

CNN's Jennifer Rizzo, Susan Candiotti and Terry Frieden contributed to this report.