The imprisoned U.S. Army private convicted of sending secret information to WikiLeaks in what is the biggest leak of classified documents in U.S. history has filed an appeal to have his 35-year prison sentence reduced to 10 years.

Bradley Manning filed a 209-page appeal on Wednesday with the U.S. Army Court of Criminal Appeals, calling his prison sentence "grossly unfair and unprecedented."

Manning, 28, who was arrested in 2010 and later convicted of violating the Espionage Act after admitting he handed over secret documents -- from the State Department and Defense Department -- to WikiLeaks, also claims in his appeal that "no whistle-blower in American history has been sentenced this harshly."

Manning's civilian attorney Vincent Ward said Manning, who now goes by the name Chelsea, was deprived of a fair court-martial because overzealous prosecutors confused the judge in their unsuccessful effort to convict Manning of aiding the enemy.

"I think that that's apparent from some of the judge's rulings in the way that she interpreted the law on all of these legal issues," Ward said in a telephone interview.

Manning was convicted of six Espionage Act violations and 14 other offenses for leaking more than 700,000 secret documents, plus some battlefield video. He is imprisoned at Fort Leavenworth, Kansas.

Lt. Col. Jennifer Johnson, an Army spokeswoman at the Pentagon, declined to comment on the substance of the appeal.

"As legal action is ongoing, we continue to maintain careful respect for the military-judicial process, the rights of the accused and ensuring the case's fairness and impartiality," she wrote in an email.

A 209-page, unclassified version of the appeal was released a day after the documents were filed with the U.S. Army Court of Criminal Appeals at Fort Belvoir, Va. It calls Manning's sentence "grossly unfair" and says the soldier's actions were those of a naive, troubled soldier who aimed to reveal the toll of the wars in Iraq and Afghanistan.

The appeal says Manning's disclosures harmed no one. At Manning's trial, prosecutors said the leaked material damaged U.S. security and put people's lives at risk by identifying informants who had helped U.S. forces.

The request for a reversal of charges is based on the harsh conditions Manning endured during nine months in a Marine Corps brig in Quantico, Va. The trial judge, Col. Denise Lind, ruled it illegal pretrial punishment and subtracted 112 days from Manning's sentence as compensation.

The appeal says Lind did not fully credit Manning "for the deplorable and inhumane conditions, which were tantamount to solitary confinement."

The appeal notes that Manning pleaded guilty to lesser offenses that could have brought up to 20 years behind bars, yet the government chose to pursue the original, more serious charges. If the charges aren't reversed, the court should reduce Manning's confinement to 10 years, as Manning's defense team recommended, the document says.

The document also challenges the constitutionality of the Espionage Act. A supporting document filed by the American Civil Liberties Union expands on those arguments, calling the act a "statute that allows the government to subject speakers and messages it dislikes to discriminatory prosecution."