Manning has been held for several months at a maximum-security pre-trial confinement facility at Quantico, Va., He will be moved to the medium-security Joint Regional Correctional Facility at Fort Leavenworth, Kan.
Defense Department general counsel Jeh Johnson said the exact date of the transfer would not be made public but it was "imminent." Johnson said a medical assessment requested by defense counsel to determine whether Manning would be mentally competent to stand trial was ongoing but the inquiry phase of that process had been completed so his transfer was possible.
He said it "may take additional time" to arrive at a medical opinion.
"At this juncture of the case, we have decided that the new joint-regional correctional facility at Fort Leavenworth, Kan., is the most appropriate facility for Private Manning for continued pre-trial detention," Johnson said.
The treatment of Manning at the Quantico facility has been criticized by his supporters, who say he was in solitary confinement 23 hours a day, made to sleep without clothes and on a suicide watch even though his mental state didn't warrant it.
Johnson said Leavenworth is appropriate for Manning's "health and welfare needs, given the possibility that he will remain in pre-trial confinement for an additional time during the 706 board process [to determine his competency] and the likelihood that the pre-trial phase of the case may continue for months beyond that."
He said Manning would be brought back to the Washington area as needed for legal proceedings. His military trial would be held in Washington.
Johnson said while Manning is presumed innocent until proven guilty, he is charged with "very serious offenses involving classified information and national security," and his continued incarceration is appropriate.
"Many will be tempted to interpret today's action as a criticism of the pre-trial facility at Quantico," he said. "That is not the case. We remain satisfied that Private Manning's pre-trial confinement at Quantico was in compliance with legal and regulatory standards in all respects, and we salute the military personnel there for the job they did in difficult circumstances."
Lt. Col. Dawn Hilton, commander of the Fort Leavenworth facility, said Manning would go through an assessment at Leavenworth for a period of five to seven days.
"After that, typically when he -- when we have finished assessing his risk, he will be housed with the other pre-trial inmates," Hilton said. "And a typical day is three square meals a day in a dining facility that the post-trials eat at. He'll receive open recreational time for 3 hours during the day, both indoors and outdoors. And he'll have the capability to interact with other pre-trial inmates on a routine basis."
Hilton said the facility has about 150 inmates, of which eight are pre-trial prisoners. Manning would not have a cellmate.