An army intelligence analyst accused of the biggest leak of classified information in US history will face a court martial.

Military District of Washington commander Major General Michael Linnington referred all charges against Private First Class Bradley Manning to a general court martial, the US Army said.

The referral means Manning, 24, who spent some of his childhood in Wales, where his mother lives, will stand trial for allegedly giving more than 700,000 secret US documents and classified combat video to anti-secrecy website WikiLeaks for publication.

The 24-year-old Oklahoma native, who went to school in Haverfordwest, faces 22 counts, including aiding the enemy - a charge which could carry life imprisonment.

A judge yet to be appointed will set the trial date.

Defence lawyers say Manning was clearly a troubled young soldier whom the army should never have deployed to Iraq or given access to classified material while he was stationed there from late 2009 to mid-2010.

At a preliminary hearing in December, military prosecutors produced evidence that Manning downloaded and electronically transferred to WikiLeaks nearly half a million sensitive battlefield reports from Iraq and Afghanistan, hundreds of thousands of diplomatic cables, and video of a deadly 2007 Army helicopter attack that WikiLeaks shared with the world and dubbed "Collateral Murder".

Manning's lawyers said others had access to Manning's workplace computers and that he was in emotional turmoil, partly because he was a gay soldier at a time when homosexuals were barred from serving openly in the US armed forces.

The defence also claims Manning's apparent disregard for security rules during training in the United States and his increasingly violent outbursts after deployment were red flags that should have prevented him from having been given access to classified material. His lawyers also contend that the material WikiLeaks published did little or no harm to national security.

The Bradley Manning Support Group, which says Manning heroically exposed war crimes, issued a statement calling his prosecution "fundamentally unjust". "This administration owes all Americans an honest explanation for their extraordinary retaliation against Bradley Manning," said Jeff Paterson, one of the group's lead organisers.