New York (CNN) -- A third man accused in a plot to bomb the New York subway system was committed to carrying out a suicide attack on U.S. soil, federal prosecutors said.
In closing arguments at Adis Medunjanin's trial in Brooklyn federal court Thursday, assistant U.S. attorney, Berit Berger, said the Bosnian-born American was willing "to strap a suicide bomb to himself, walk into a New York City subway and blow it up."
Berger told jurors that al Qaeda leaders assigned the mission to Medunjanin during a 2008 trip he took to Pakistan with two high school friends, Najibullah Zazi and Zarein Ahmedzay.
But in his closing, Medunjanin's attorney, Robert Gottlieb, said his client's travel to Pakistan was "not to join al Qaeda, but to join the Taliban in fighting foreign troops in Afghanistan.
Gottlieb said Medunjanin wanted to join the Taliban to stand up for Muslims and defend his religion. He called the three young men, "immature, naive and clueless" when they set out to travel to Afghanistan.
"They wanted to fulfill some romantic version of jihad," Gottlieb said.
Prosecutors said he conspired with his two friends to detonate explosives in subways in 2009.
But Gottlieb denies his client had a role in the bomb plot.
Medunjanin has pleaded not guilty to charges that include conspiring to use weapons of mass destruction and conspiring to provide material support to al Qaeda. He faces life in prison if convicted.
Co-conspirators Zazi, an immigrant from Pakistan, and Ahmedzay, an immigrant from Afghanistan, have pleaded guilty to planning the attack with him and are awaiting sentencing.
Zazi and Ahmedzay have cooperated with the government and testified last week at Medunjanin's trial.
A jury is expected to begin deliberations on Monday.