Chelsea Manning has responded to Donald Trump's ban on transgender people serving in the US military, accusing the President of "cowardice".
Mr Trump claimed "tremendous medical costs and disruption" were behind the move, which bars transgender people from serving "in any capacity".
Transgender service members have been able to serve openly in the military since last year, when Barack Obama's Defence Secretary ended the ban.
The President made the announcement in a string of tweets on Wednesday morning, saying that after consulting with "generals and military experts," the government "will not accept or allow transgender individuals to serve in any capacity in the US military."
It is not clear what impact the new measure will have and whether it will apply to those already serving in the armed forces. A Pentagon spokesman refused to answer questions about the measure.
"Call the White House," Navy captain Jeff Davis said when asked.
Responding to the surprise announcement, Ms Manning said: "So, biggest baddest most $$ military on earth cries about a few trans people but funds the F-35? Sounds like cowardice."
The former soldier, who was released from prison in May after serving seven years for disclosing secret military documents to WikiLeaks, said the armed forces "have always been a social experiment just as much as a fighting force".
In a later tweet, she suggested that the move showed military funding should be diverted into an improved healthcare system.
Meanwhile, Stephen Peters, a spokesman for LGBT advocacy group the Human Rights Campaign said the President's decision was "morally reprehensible," "patently unpatriotic" and dangerous because it put "a target on the backs of thousands of service members".
Campaign group Vets Against Trump said in a series of statements on Twitter: “You don’t know anything about service. Shame on you.
“You are dishonouring people who, unlike you, actually donned the uniform to serve their nation.
It added: “The greatest 'burden' on our military is a reckless, ignorant CIC who dishonours the office and actively undermines our national security."
Ash Carter, who as secretary of defence last year ended the ban on transgender people serving openly in the military, criticised Mr Trump's decision.
"To choose service members on other grounds than military qualification," he said, "is social policy and has no place in our military."
Mr Carter added that transgender individuals already are serving capably and honorably in the military.
Associated Press contributed to this report
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