"I am Chelsea Manning. I am female,” the Army private said in the statement, which was read aloud by Manning's attorney on Today.
"Given the way that I feel, and have felt since childhood, I want to begin hormone therapy as soon as possible. I hope that you will support me in this transition.”
"I also request that, starting today, you refer to me by my new name and use the feminine pronoun (except in official mail to the confinement facility).
"I look forward to receiving letters from supporters and having the opportunity to write back.”
Manning was sentenced Wednesday to 35 years in prison for giving hundreds of thousands of secret military and diplomatic documents to WikiLeaks in one of the biggest leak cases in the U.S. since the Pentagon Papers a generation ago.
With good behavior and credit for the more than three years he has been held, Manning could be out in about 6 ½ years, according to his defense attorney David Coombs.
Coombs told a press conference at a nearby hotel that early next week he'll file, through the Army, a request that the president pardon the soldier "or at the very least commute" the sentence to time already served.
"The time to end Brad's suffering is now," Coombs said. "The time for our president to focus on protecting whistleblowers instead of punishing them is now."
The former intelligence analyst was found guilty last month of 20 crimes, including six violations of the Espionage Act, as part of the Obama administration's unprecedented crackdown on media leaks.
He was acquitted of the most serious charge, aiding the enemy, which carried a potential life in prison without parole.