An indictment unsealed in New York said Ethan Phelan Melzer, 22, was serving in the US Army in Vincenza, Italy, and expecting to go to Turkey when he offered an FBI informant he believed had ties to jihadist groups detailed information on his unit's movements last month.

In online chatrooms for the neo-Nazi and satanist Order of the Nine Angles, or O9A, he detailed their planned location and armaments in Turkey, suggesting attackers could easily overcome the force, according to the indictment.

Melzer made clear he was supporting a "jihadist" attack on the unit, and that he himself might die.

"I would've died successfully...Cause if another 10-year war in the Middle East would definitely leave a mark," he told the informant.

Melzer was charged with six counts of plotting to murder his fellow soldiers and material support to terror groups. The indictment said the Louisville, Kentucky native enlisted in the army in 2018 and had joined the violent O9A at least as early as 2019.

He shared information on his unit's movements with fellow O9A followers and a related group called the "Rapewaffen Division" "for the purpose of facilitating an attack on the unit," the Justice Department alleged.

After his arrest, "Melzer declared himself to be a traitor against the United States, and described his own conduct as tantamount to treason," it said in a statement.

If found guilty he faces up to life in prison.