PORTLAND, Ore. >> A young Somali American was sentenced Wednesday to 30 years in prison for plotting to detonate a bomb in Portland’s downtown square while 10,000 revelers gathered to watch the mayor light a towering Christmas tree.

Prosecutors had sought a 40-year term for Mohamed Mohamud, 23, in the 2010 plot that actually was an FBI sting. But U.S. District Court Judge Garr King said Mohamud’s youth and remorse for his actions helped lower his sentence.

King said he believes the actions of undercover FBI agents edged into “imperfect entrapment,” the idea that though they didn’t fully entrap Mohamud in a legal sense, their actions nonetheless encouraged him to commit wrongdoing.

“This is a sad case,” King said.

Mohamud was arrested Nov. 26, 2010, after pressing a keypad button on a cellphone that he believed would trigger a massive truck bomb and kill people gathered for the annual holiday event. But the bomb was a fake provided by FBI agents posing as al-Qaida recruiters.

The undercover agents made friends with Mohamud after learning he had written for an online jihadi magazine and exchanged emails with accused terrorists.

King disagreed with defense attorneys who made a last-gasp effort to portray Mohamud’s actions as those of a confused teenager who just had his braces removed when first contacted by an FBI agent posing as a member of a terrorist cell.

Mohamud chose the location and timing of the bomb, King said, and when offered the choice to commit peaceful acts of resistance, he instead told the undercover agents he wanted to “become operational.”

Mohamud’s defense team had sought a term of no more than 10 years, and said he will appeal the sentence.

The former Oregon State University and his parents spoke before he was sentenced.

“The things I said and did were terrible,” Mohamud said. “The hardest thing is to go over the (undercover agents’) tapes, to see myself, to hear what I was saying.”

His mother, Mariam Barre, begged the judge for leniency.

“Give him another chance,” she said through tears on the witness stand.

His father, Osman Barre, said he has watched his waifish teenage son become an adult in prison and mature in the process. But King said Mohamud’s youth aside, the sentence had to both punish him for his actions and serve as a warning for anyone planning similar acts.

FBI director James Comey said Wednesday that King’s remarks about “imperfect entrapment” will have no effect on the agency’s sting operations.

Comey was in Portland as part of a national tour of field offices — the U.S. Attorney’s Office for Oregon says his presence on the day of Mohamud’s sentencing was a coincidence.

Osman Barre was the first person to alert the FBI of his son’s early leanings toward violent jihad, something he later said he regretted. The alert led the FBI to launch its sting operation.

Comey said Wednesday that parents in a similar situation ultimately have no other recourse, and he’s unsure whether Mohamud’s case would discourage them from coming forward.

“I just don’t know what the alternative is,” Comey said.

Jurors rejected Mohamud’s entrapment defense at his January 2013 trial. The sentencing was pushed back a year after the government disclosed that warrantless overseas wiretaps helped make its case. The defense unsuccessfully sought a new trial.

–Nigel Duara / Associated Press. Associated Press writer Steven Dubois contributed to this report.