WikiLeaks suspect Bradley Manning was placed in solitary confinement in a military prison to protect him from possible attacks from "patriotic" inmates, the Marine brig commander said Thursday.

James Averhart, in charge of the brig at the Marine base in Quantico, Virginia, where Manning was held for nine months, said the suspect was held as a "maximum security prisoner" for his own safety.

"A lot of the population was very patriotic, and knew about the allegations" against Manning, Averhart said. "It was my responsibility if something could happen outside the [maximum security] facility to Manning."

Averhart testified at a pre-trial hearing at Fort Meade, an army base just outside the US capital, investigating the conditions in which Manning was held.

Manning, 24, was serving in Iraq as a US army intelligence analyst when he was arrested in May 2010. He is accused of passing Iraq and Afghanistan war logs plus thousands of diplomatic cables to Julian Assange's anti-secrecy website.

After he was arrested and questioned in Iraq, Manning was sent to a US jail in neighboring Kuwait but was transferred to the Marine brig at Quantico, Virginia two months later.

Manning was held at Quantico for nine months until April 2011, and then transferred to a US Army prison at Fort Leavenworth, Kansas.

Manning's civilian attorney David Coombs wants the case dropped, arguing that the detention conditions at Quantico -- in which Manning was held under 24-hour suicide watch in a tiny cell, allowed only 20 minutes of sunlight a day, and stripped naked at night -- amounts to "unlawful pretrial punishment."

Averhart testified Thursday that other factors were taken into account when deciding to hold Manning under such strict conditions, including his "depression" and "anxiety" over the charges that he faced.

Manning could spend the rest of his life behind bars if found guilty of "aiding the enemy."

His case is expected to go on trial in March 2013.