Bradley Manning trial begins 3 years after arrest

Manning is charged in the biggest leak of classified information in US history

Army Pfc Bradley Manning goes on trial today more than three years after he was arrested in Iraq and charged in the biggest leak of classified information in US history.

Manning has admitted to sending troves of material to the anti-secrecy website WikiLeaks and pleaded guilty to charges that would send him to prison for up to 20 years. The US military and the Obama administration weren't satisfied, though, and pursued a charge of aiding the enemy, which carries a potential life sentence.

The trial on that most serious charge and 20 other offences begins today for the 25-year-old former intelligence analyst from Oklahoma. It's the most high-profile case for an administration that has come under criticism for its crackdown on leakers. The six prosecutions since Obama took office is more than in all other presidencies combined.

Manning chose to have his court-martial heard by a judge instead of a jury. It is expected to run all summer.

In February, Manning told military judge Army Col Denise Lind that he leaked the material to expose the American military's "bloodlust" and disregard for human life in Iraq and Afghanistan. He said he did not believe the information would harm the US and he wanted to start a debate on the role of the military and foreign policy.

The judge accepted his guilty plea to reduced charges for about half of the alleged offences, but prosecutors did not and moved forward with a court-martial on charges including violations of the Espionage Act and the Computer Fraud and Abuse Act.

Manning's supporters hail him as a whistleblowing hero and a political prisoner. Others view him as a traitor.

US officials have said the more than 700,000 Iraq and Afghanistan battlefield reports and State Department cables sent to WikiLeaks endangered lives and national security.

The material WikiLeaks began publishing in 2010 documented complaints of Iraqi detainee abuses; a US tally of civilian deaths in Iraq; and America's weak support for the government of Tunisia a disclosure Manning supporters said encouraged the popular uprising that ousted the Tunisian president in 2011 and helped trigger the Middle Eastern pro-democracy uprisings known as the Arab Spring.

Last month, the government agreed to accept Manning's guilty plea for one lesser version of one count, involving a single diplomatic cable summarising US embassy discussions with Icelandic officials about the country's financial troubles.

Manning also acknowledged sending WikiLeaks unclassified video of a 2007 US Apache helicopter attack that killed civilians, including a Reuters photographer. An internal military investigation concluded the troops reasonably mistook the camera equipment for weapons; WikiLeaks dubbed the video "Collateral Murder.