Ikaika Erik Kang, 35, whose sentence was part of a plea agreement, will also be under at least 20 years of supervised release after he completes his prison term.

"Kang swore to defend the United States as a member of our military, but betrayed his country by swearing allegiance to ISIS and attempting to provide it material support," John Demers, assistant attorney general for national security, said in a statement.

According to authorities, Kang, a sergeant in the US Army, became sympathetic to ISIS by at least early 2016 and regularly watched propaganda videos published online by the terror group while expressing a desire to become a member.

Prosecutors said he spoke in detail about committing specific acts of violence including launching attacks at public gatherings such as the Honolulu Christmas Parade and planning a suicide bombing at his army barracks.

In June and July of last year, he met with undercover FBI agents posing as people with connections to ISIS and provided them with sensitive material.

He also supplied the agents with a small aerial drone and military-style clothing and gear.

On another occasion, he provided two undercover FBI employees -- one pretending to be a high-ranking ISIS leader and another an ISIS fighter -- with a two-hour combat training session to hone their fighting and marksmanship skills.

Kang was arrested after he swore allegiance to ISIS during a ceremony conducted by the purported ISIS leader.

"This is the first case in the state of Hawaii where someone was convicted for providing material support to terrorism," said Sean Kaul, special agent in charge of the FBI office in Honolulu. "This should serve as reminder that even though we are 2,500 miles from the US mainland these crimes can and do happen everywhere."

According to local media, Kang grew up in an abusive household and his father suffered from mental health issues. Two former members of the US military also testified that he had mental health issues and could easily be influenced.