Manning provided a copy of the subpoena document to the New York Times during an interview on Friday.
The order was issued by the Eastern District of Virginia, the same district where prosecutors unintentionally exposed secret charges against Assange in an unrelated filing in November. Manning is required to appear on March 5.
“Given what is going on, I am opposing this,” she said. “I want to be very forthright I have been subpoenaed. I don’t know the parameters of the subpoena apart from that I am expected to appear. I don’t know what I’m going to be asked.”
Manning explained that her legal team would file a motion to argue that forcing her to appear would violate her constitutional rights but did not specify whether she would cooperate if the motion failed.
Manning’s efforts are being supported by activists through a new committee called Chelsea Resists, which will fundraise and bring awareness to the whistleblower’s fight.
“I am not going to contribute to a process that I feel is dangerous and could potentially place me in a position where I am forced to backtrack on the truth,” Manning told the Times.
As an intelligence analyst in 2010, Manning leaked nearly 750,000 diplomatic cables to WikiLeaks. The enormous cache included the infamous 2007 “Collateral Murder” video showing a U.S. attack helicopter killing two Reuters journalists in Iraq.
Manning’s 2013 conviction resulted in a 35-year prison sentence that was commuted after seven years by former President Barack Obama.
Assange, meanwhile, has resided at the Ecuadorian embassy in London since 2012 in a bid to avoid U.S. extradition. He was known to have been under investigation by the Justice Department since WikiLeaks published Manning’s leaked cache, but November’s slip up by federal prosecutors inadvertently exposed that sealed charges existed against him.
The Justice Department refuses to “confirm or deny the existence of criminal charges” in Assange’s case.