A disciplinary board at the Fort Leavenworth, Kansas, military prison where Manning is incarcerated informed her of the decision after a hearing on Thursday, according to a statement by support group "Fight for the Future."

The punishment - of 14 days isolated from any human contact in a separate cell - follows a suicide attempt and being found with a banned book "Hacker, Hoaxer, Whistleblower, Spy," by Gabriella Coleman, in her cell.

Manning's lawyer Nancy Hollander described the punishment as "extremely worrisome" and "counterproductive to Chelsea's mental and physical health."

"Essentially she is now being tortured as punishment for an act of desperation," Hollander said.

No date was given for the sentence to start.

Manning was quoted in the support group statement saying she could appeal the punishment, and that seven days of it would be suspended provided she stayed out of trouble for six months.

"I am feeling hurt. I am feeling lonely. I am embarrassed by the decision. I don't know how to explain it," Manning said, having tried to take her own life after what her lawyers said was the Army's denial of appropriate healthcare.

Suicide attempt and fasting protest

Earlier this month, Manning went on a hunger strike, agreeing to end it only when the Army said she would be allowed to receive gender transition surgery. She began hormone therapy in 2015.

Following Thursday's decision, Army spokesman Wayne Hall said in an email: "It would be inappropriate for the Army to comment at this time."

Manning has been a focus of a worldwide debate on government secrecy since she provided more than 700,000 documents, videos, diplomatic cables and battlefield accounts to the anti-secrecy group WikiLeaks.

She was arrested in 2010 as Bradley Manning, an intelligence analyst in Iraq, and was convicted in 2013 in a military court.

The case ranked as the biggest breach of classified materials in US history and drew a 35-year jail sentence.

mm/kl (AP, Reuters)