ALEXANDRIA, Va. – A United Nations official says the continued incarceration of former intelligence analyst Chelsea Manning for her refusal to testify to a grand jury amounts to torture.

The U.N.’s special rapporteur on torture released a letter Thursday to U.S. officials in support of Manning.

Manning was subpoenaed last year to testify to a grand jury investigating WikiLeaks.

Manning says she opposes the grand jury system and won’t testify.

Prosecutors have said that Manning faces the same obligations as all citizens to comply with lawful subpoenas, and that she can end her jail term at any time by agreeing to testify.