CHICAGO (AP) — A federal judge scolded a former college student from suburban Chicago as he sentenced him to a maximum 15-year prison term Thursday for seeking to join terrorist-linked militants fighting Bashar Assad's regime in Syria, saying he would have given him even more time behind bars if statutes allowed it.

The judge brushed aside arguments by Abdella Ahmad Tounisi's lawyers who said the then-18-year-old's plans for Syria in 2013 didn't neatly fit the definition of terrorism. They insisted he'd been motivated foremost by a sincere desire to help Syrians by fighting Assad's repressive regime — not by any extremist ideology.

"You traded your opportunity to attend college for a terrorist training camp," Judge Samuel Der-Yeghiayan said, addressing Tounisi directly. "You chose to join a bunch of thugs who took pride in cowardly killings."

He then added sternly: "There are no free passes when it comes to collusion with terrorists."

The judge said the group Tounisi aspired to join, Jabhat al-Nusrah, wasn't merely one of many militant organizations seeking to oust Assad — some of which the United States has supported. It was one affiliated with al-Qaida, which has "openly called for the destruction of this nation," Der-Yeghiayan said.

Tounisi, of Aurora, Illinois, apologized in a brief statement before he was sentenced, speaking softly and looking younger than his 23 years. After reflection in jail, he said, he's now grateful federal agents arrested him at Chicago's O'Hare International Airport on April 19, 2013, before he could start his journey to participate in the civil war in Syria.

"Thank you," he said. "Thank you for saving my life."

As the hearing began, a child sitting on Tounisi's father's lap smiled when he saw Tounisi led into the room and shouted, "Hi Abdella!" Tounisi, standing with his legs shackled, later hung his head when the judge imposed the toughest punishment available under U.S. law. Several of his relatives in court also looked shaken.

Tounisi pleaded guilty in 2015 to attempting to provide material support to terrorists. Defense attorneys had asked for a seven-year prison term, which with time served could have led to his release from prison within two or three years.

While the U.S. attorney's office asked in filings for a 15-year term, prosecutor Barry Jonas sounded conciliatory Thursday compared to the judge. Jonas told Der-Yeghiayan he accepted that Tounisi was "extremely remorseful" and said the court could consider it in calculating a sentence.

Tounisi's case also focused attention on the use of fake extremist sites created by the FBI. Critics say they tend to woo and then ensnare impressionable youth, like Tounisi, while others argue they stop terrorist wannabes in the virtual world before they can carry out real-world harm.

Tounisi visited one such sham site just weeks before his 2013 arrest. It included photos of gun-toting fighters and a flowery exhortation to, "Come and join your lion brothers ... fighting under the true banner of Islam." Soon after, he began communicating with federal agents posing as militants.

Der-Yeghiayan also ordered that Tounisi will be subject to lifetime supervision once released, including close monitoring of his internet use.

Tounisi, born in Massachusetts to Jordanian immigrant parents and raised in the Chicago area, was feeling increasingly isolated as a Muslim in the United States, one of his lawyers said in court and presentencing filings.

"His deep desire to belong and his youth was, in some way, exploited by the agents," attorney Molly Armour said. "Instead of pushing him towards a productive use of his life, he was encouraged (to become more isolated) and take a different path."

But Jonas noted Tounisi had been questioned in the 2012 arrest of his friend, Adel Daoud, in a separate sting for allegedly trying to bomb a Chicago bar. Despite the visit and interrogation by the FBI on the day of Daoud's arrest, Tounisi still hatched plans months later to join an al-Qaida-linked group.

The visit by FBI agents "should have scared him straight," Jonas said. "But it didn't. It only emboldened him."

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Follow Michael Tarm on Twitter at http://twitter.com/mtarm