"No matter what happens today ... whether i'm placed in confinement or not, I'm not going to comply with this grand jury," Manning said.
Chelsea Manning announced Thursday that she will again refuse to cooperate with a grand jury investigating a release of documents by WikiLeaks.
Manning made the declaration in a press conference before walking into a federal courthouse in Alexandria, Virginia.
"No matter what happens today ... whether I'm placed in confinement or not, I'm not going to comply with this grand jury," the U.S. Army whistleblower said.
The threat of being locked up, Manning said, will have no effect on her.
"It doesn't frighten me or disturb me," she said. "I mean, I've already been to jail. I've already been to prison, so attempting to coerce me with a grand jury subpoena is just not going to work."
Earlier this month, Manning was freed after 62 days in a Virginia jail after her refusal to testify before a previous grand jury in the WikiLeaks case.
She was released when the term of that grand jury expired. But then Manning was ordered to appear before a different panel in Alexandria on Thursday.
Federal prosecutors in Alexandria recently unsealed an indictment issued in secret in late 2017 against WikiLeaks founder Julian Assange, who had been holed up in Ecuador's embassy in London before his arrest by British authorities last month.
Manning, a former Army intelligence analyst, has said she objects to the secrecy of the grand jury process.
She also claims to have revealed everything she knows about WikiLeaks at her court-martial, where she was found guilty of or leaking a trove of military and diplomatic documents to the anti-secrecy website.
Manning was sentenced to 35 years behind bars and served seven years of that term before then-President Barack Obama commuted her sentence.
"The goal here is to re-litigate the court-martial," she said Thursday. "They didn't like the outcome, I got out. This is a way of placing me back into confinement."