By Nate Raymond

NEW YORK (Reuters) - A New York man was sentenced on Tuesday to 13 years in prison for trying to join the Islamic militant group al Qaeda when he was a high school senior.

Justin Kaliebe, now 22, was sentenced by U.S. District Judge Denis Hurley in Central Islip, New York, after pleading guilty in February 2013 to having attempted to provide material support to al Qaeda in the Arabian Peninsula.

Kaliebe had been arrested a month earlier at John F. Kennedy International Airport, where prosecutors said he planned to board a flight to Muscat, Oman, as part of his plot to eventually travel to Yemen.

The defendant was also sentenced to 20 years of supervised release.

"I am disappointed and feel that a lesser sentence was warranted," Kaliebe's lawyer Anthony LaPinta said in an email.

"Justin is a harmless young man who had many psychological, medical and personal issues that contributed to his criminal conduct," LaPinta continued. "Justin will make the best of his time in prison. I am certain that he will emerge as a rehabilitated, productive and respected member of society."

Federal authorities have estimated that 80 percent of Americans linked to activities supporting militant Islamic movements have radicalized themselves with information from the internet.

Prosecutors said Kaliebe, a resident of Babylon, New York, began his plot in 2011, and told an undercover law enforcement operative the following year that he was "doing the J word," or violent "jihad."

In June 2012, Kaliebe was recorded as saying that upon arriving in Yemen, he expected to fight "those who are fighting against the Sharia of Allah," be it the Yemeni army or U.S. forces, prosecutors said.

Kaliebe received support from Marcos Alonso Zea, another Long Island resident who according to prosecutors attempted to fly to Yemen in January 2012 but was intercepted by British customs officials and returned to the United States.

Zea, 28, was arrested in October 2013 and sentenced in April 2015 to 25 years in prison, after pleading guilty to attempting to provide material support to a foreign terrorist organization.

(Reporting by Nate Raymond in New York; Additional reporting by Jonathan Stempel; Editing by Tom Brown)