A bearded Muhanad Mahmoud Al Farekh, wearing light blue prison attire, said nothing and entered no plea during a brief court appearance Thursday afternoon before a federal judge in Brooklyn. He was ordered held without bail.
His attorney did not comment.
"Today's arrest demonstrates that there is no escape from the long reach of our law for American citizens who seek to do harm to our country on behalf of violent terrorists," Brooklyn U.S. Attorney Loretta Lynch said in a statement.
Al Farekh, who was born in Texas, and two other co-conspirators were students at the University of Manitoba in Winnipeg, Canada, in 2007 when authorities say they started watching al-Qaida propaganda and hatching a plan to become martyrs abroad, an FBI agent wrote in a January complaint.
Al Farekh and the two others flew to Karachi, Pakistan, on round-trip tickets in March 2007 after selling their belongings, disconnecting their phones and buying mountain boots that authorities say are commonly worn by al-Qaida fighters in Pakistan and Afghanistan, the complaint says.
One of Al Farekh's co-conspirators, Canadian citizen Ferid Imam, trained three men on how to use AK-47s and other weapons at an al-Qaida training camp in 2008, the complaint says. The three — Najibullah Zazi, Zarein Ahmedzay and Adis Medunjanin — were later convicted of plotting to bomb New York City's subway system and are co-operating with federal authorities. Imam, who went by the name "Yousef," has been indicted on separate terrorism charges.
In 2009, the third Canadian co-conspirator sent a letter to his relatives, encouraging them to come to Pakistan, the complaint says.
"If you decide to come to Pakistan don't tell them that you are coming to meet me," he wrote, according to the court documents. "And if your plan is to come to Pakistan to try and talk to me of going back with you then I swear by Allah (s.w.t) that will never happen."
Associated Press writers Tom Hays and Larry Neumeister contributed to this report.