Former Army intelligence analyst Chelsea Manning speaks with reporters after arriving at court on Thursday in Virginia. (Cliff Owen/AP)

Former Army intelligence analyst Chelsea Manning is challenging steep fines imposed on her by a federal judge for refusing to testify before the grand jury investigating WikiLeaks founder Julian Assange.

Last weekend, Manning started paying a daily $500 fine. After 30 days, the charge will rise to $1,000 a day. She could remain incarcerated for another 15 months.

“The cumulative fines are so far beyond her ability to pay that they are essentially meaningless,” her lawyers wrote in a filing Thursday in Alexandria federal court.

Although Manning was supporting herself as a public speaker before her incarceration and has a deal to write a book, according to her lawyers, she lost that revenue when she went to jail in March and has given up her apartment because she cannot pay her rent.

Assange has been indicted on charges he engaged in a conspiracy with Manning in 2010 to disseminate classified information and anonymously access a Defense Department computer. Manning served seven years in a military prison for the disclosures.

Prosecutors asserted in a filing last week that they want information from Manning that goes beyond her interactions with Assange.

“Manning’s testimony remains relevant and essential to an ongoing investigation into charges or targets that are not included in the superseding indictment,” they wrote. “The offenses that remain under investigation are not time barred.”

Most federal crimes have a five-year statute of limitations. The Espionage Act can be charged up to a decade after an alleged breach.

Prosecutors have also argued that the fines are appropriate because Manning can and has raised money on social media to support herself. Along with her upcoming memoir, she was recently featured in a documentary on Showtime. Her lawyers say the money she has raised covers only a fraction of what she will owe if she pays the daily fines for the rest of the 18-month grand jury.

Moreover, they argue the fines will not have the desired effect of persuading her to testify.

“She continues to aver that she will never relent, and that any proposed fines will not move her,” they wrote.

Manning is prepared to offer bank statements proving her lack of funds, they say, and is asking for a hearing to make her case.