WikiLeaks suspect Bradley Manning declined to enter a plea at his arraignment Thursday on charges of turning over a massive cache of classified US documents to the secret-spilling site.

Manning, a 24-year-old US Army private, is charged with 22 counts in connection with one of the biggest intelligence breaches in US history.

The most serious charge -- "aiding the enemy" -- could send him to prison for life.

Dressed in an army uniform and flanked by his lawyers, Manning was mostly silent during the 45-minute arraignment at this sprawling army base outside of Washington.

He responded "Yes, your honor" when asked by military judge Denise Lind whether he understood his rights and the charges against him.

Manning deferred entering a plea, which he is not required to do until the start of the court-martial. He also declined to say whether he preferred to be tried before a single military judge or a military jury.

During the hearing, the judge asked attorneys for the prosecution and the defense when they wanted the trial to begin.

Army prosecutors opted for an August 3 start date but Manning's civilian attorney, David Coombs, asked for the court-martial to begin in June.

"As of today, Bradley Manning has been in confinement for 635 days," Coombs said.

As the hearing adjourned, a member of the activist group Code Pink shouted out, "Judge, isn't a soldier required to report a war crime?"

Manning is accused of passing hundreds of thousands of military field reports from Iraq and Afghanistan and US diplomatic cables to WikiLeaks between November 2009 and May 2010, when he served as an intelligence analyst in Iraq.

The leak of the military documents shed light on civilian deaths, while the diplomatic cables sparked a firestorm by disclosing the private remarks of heads of state and candid observations by senior US officials.

The US government slammed the disclosure of the documents by WikiLeaks, saying it threatened national security and the lives of foreigners working with the military and US embassies.

WikiLeaks supporters view the site as a whistleblower that exposed US wrongdoing and see Manning as a political prisoner.

Army investigators told a hearing in December that contact information for WikiLeaks founder Julian Assange, military reports, cables and other classified material had been found on computers and storage devices used by Manning.

Manning's defense attorneys have portrayed him as suffering from "gender identity disorder" and had created an online female alter ego called "Breanna Manning."

The Bradley Manning Support Network said this month that Manning had been nominated for the Nobel Peace Prize by members of the Icelandic parliament.

It is not possible to verify who has been nominated for the awards.

Assange has meanwhile been in Britain fighting extradition to Sweden, where he faces sexual assault accusations.

He has denied the allegations, saying they are politically motivated.