Bradley Manning's letter, entitled The Next Stage of My Life, was signed with a handwritten signature in the name of Chelsea Manning.
The letter was broadcast on NBC's Today show as Manning's lawyer revealed the soldier's desire to live life as a woman.
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White House budget officials outlined the information during a telephone call with reporters given on condition of anonymity.
A prison officer is to be charged with gross negligence manslaughter and misconduct in public office in relation to the death of an inmate.
The 2017 Oscars will be remembered as the year the wrong film got the best picture award, but it wasn't the first memorable mix-up.