(CNN)-- A key witness is expected to testify Tuesday as the trial of a Bosnian immigrant accused of plotting to bomb New York's subway system continues.
Adis Medunjanin is accused of devising a terror plot with two other men. One of the co-defendants, Najibullah Zazi, is expected testify Tuesday, court officials said.
During opening statements Monday, a federal prosecutor described Medunjanin as an "al Qaeda terrorist," an assertion the defense said was "just wrong."
Along with his co-defendant, an extensive roster of convicted terrorists are lined up to testify against Medunjanin during his trial in New York.
Prosecutors allege that Medunjanin traveled to Pakistan's tribal belt with two friends, where he sought to join the Taliban but ended up being recruited by al Qaeda to perform a suicide mission back in America.
He and the two others, they claim, eventually hatched a plan to rig backpacks with explosives and blow them up on New York subway stations.
Medunjanin's co-defendants -- Zarein Ahmedzay, an immigrant from Afghanistan, and Zazi, an immigrant from Pakistan -- have already pleaded guilty to the same charges.
"In September of 2009, three men were prepared to strap bombs to their bodies and go into crowded subways," Assistant U.S. Attorney James Loonam told jurors in his opening statement Monday.
"These men were al Qaeda terrorists," Loonam claimed.
Angry at the presence of U.S. troops in Afghanistan and Iraq, the three went to Pakistan's tribal belt -- "the center of al Qaeda activity against the United States" -- to join the terrorist group, according to Loonan.
Once there, the federal prosecutor said, the men were given "special treatment" and "private training by al Qaeda" because of their coveted status as U.S. citizens.
In his opening statement, defense attorney Robert Gottlieb accused the prosecution of using incendiary rhetoric to inflame the jury.
"These are all words the government knows will scare you beyond belief and shake you to the core," Gottlieb said of terms like "terrorist" and "al Qaeda."
"The truth is Adis Medunjanin is not a terrorist. ... In this case, the government is just wrong."
Later Monday, Ahmedzay took the stand and described how his former high school classmate Medunjanin turned him on to the teaching of radical cleric Anwar al-Awlaki. The American-born Muslim cleric was targeted and killed in a September 2011 drone attack in Yemen.
Medunjanin's trial is expected to last three weeks.