Chelsea Manning, the former U.S. military officer jailed for a massive leak of U.S. secrets to WikiLeaks, has been ordered to appear before a grand jury, her attorney said Friday. Moira Meltzer-Cohen said she had not been told what the grand jury was investigating, but U.S. media have speculated that it might involve the criminal case against WikiLeaks being developed by federal prosecutors in Virginia. Meltzer-Cohen said Manning had filed a motion to challenge the subpoena, which was immediately put under seal in the case. "I object strenuously to this subpoena, and to the grand jury process in general," Manning, 31, said in a statement. Grand juries, used only in the U.S. and Liberia, are groups of citizens operating separately from courts who investigate whether to bring criminal charges. They can compel witnesses and suspects to testify. "We've seen this power abused countless times to target political speech," added Manning. "I have nothing to contribute to this case and I resent being forced to endanger myself by participating in this predatory practice." Manning, a former army intelligence analyst, was jailed for 35 years in 2013 for giving WikiLeaks more than 700,000 classified documents related to the wars in Iraq and Afghanistan. Misdeeds exposed The revelations by Manning, who is transgender and was then known as Bradley Manning, exposed covered-up misdeeds and possible crimes by U.S. troops and allies. Her actions made her a hero to anti-war and anti-secrecy activists, but U.S. establishment figures branded her a traitor. They also made WikiLeaks a force in the global anti-secrecy movement. Then-President Barack Obama commuted her sentence, leading to her release in May 2017. Manning is scheduled to appear in front of the grand jury on Tuesday. The New York Times and Politico both speculated it was related to the U.S. investigation of WikiLeaks in relation to its publication of Democratic campaign secrets in 2016 that the U.S. government says were hacked by Russian intelligence. The Justice Department has not confirmed it is developing a case against WikiLeaks and its founder, Julian Assange. But a mistaken assertion in filings for a separate case in the Virginia court made distinct reference to the WikiLeaks probe.