NEW YORK (Reuters) – A second Afghan-born man pleaded guilty on Friday of plotting to attack subways in New York, in what U.S. officials said was the most serious threat to the city from the attacks of September 11 2001.

Zarein Ahmedzay The driver pleaded guilty in federal court in Brooklyn of conspiring to use weapons of mass destruction, conspiracy to commit murder in a foreign country and provide material support Al Qaeda of Osama bin Laden.

Ahmedzay, 25, is a former high school teammate in the United States Zazi Najibullah, who this year admitted to receiving weapons and training from Al Qaeda and planning a suicide bombing in the underground city.

Prosecutors said the men planned to carry out the attack during the Islamic holy month of Ramadan, between 22 August and on 20 September last year, but abandoned the plot when they learned they were being investigated.

Zazi, who moved to Queens in New York from Afghanistan as a teenager, will sentenced in June. Ahmedzay”s sentence was set for July. Both men could receive life imprisonment.

Ahmedzay, who is a U.S. citizen, admitted that he traveled to Pakistan in 2008 with Zazi, where both men were trained in making bombs for Al Qaeda.

“I was a New York taxi driver and knew the city well. The most important impact was best-known structures and maximize the number of deaths,” said U.S. Judge Ahmedzay Steve Gold .

“I personally believe that an operation in the United States would be the best way to end war,” he said.

(Reporting by Edith Honan, editing by Marion Giraldo Spanish)