In the news conference, Pentagon officials insisted that his move had nothing to do with his treatment at Quantico. They characterized the transfer to the medium security Leavenworth facility, which opened in January, as simply a better place to hold prisoners who, like Private Manning, are awaiting trial.

“Many will be tempted to interpret today’s action as a criticism of the pretrial facility at Quantico,” Jeh C. Johnson, the Pentagon’s general counsel, said. “That is not the case. We remain satisfied that Private Manning’s pretrial confinement at Quantico was in compliance with legal and regulatory standards in all respects.” Nonetheless, Mr. Johnson said that “we have determined the new pretrial facility at Fort Leavenworth is the most appropriate one for Private Manning going forward.”

Lt. Col. Dawn Hilton, the garrison commander at Fort Leavenworth, was highly enthusiastic in her descriptions of what would soon be Private Manning’s new location. “I encourage you to come out and see how wonderful our facility is,” she told reporters at the briefing. Both she and Mr. Johnson promised tours for the media.

Colonel Hilton said that mental health professionals at Leavenworth would conduct an assessment of Private Manning once he arrives. Assuming he is not determined to be a danger to himself and others, she held out the possibility that he would eat three meals a day in a group dining hall, have three hours daily of recreation time, both indoors and out, and be permitted to interact with other prisoners.

President Obama and other administration officials have defended Private Manning’s treatment at Quantico, but Philip J. Crowley resigned as the State Department spokesman last month after publicly criticizing the Pentagon as “’ridiculous and counterproductive and stupid” in its treatment of him.