The civilian lawyer for Private Bradley Manning, the US soldier accused of leaking classified documents published by WikiLeaks, has asked the presiding officer at his pre-trial hearing to step aside.

Lt Col Paul Almanza's civilian occupation as a Justice Department prosecutor was the chief reason defence lawyer David Coombs gave for asking him to stand aside.

Manning, 23, is charged with aiding the enemy by leaking hundreds of thousands of secret documents that ended up on the website. At the time, he was a low-level intelligence analyst in Baghdad.

The case has spawned an international movement in support of Manning, who is seen by anti-war activists as a hero who helped expose American mistakes in Iraq and Afghanistan.

But to others he is a villain, even a traitor, who betrayed his oath of loyalty by deliberately spilling his government's secrets.

The hearing was to determine whether Manning will face a court-martial. If his case goes to trial and he is convicted, Manning could face life in prison though the government has said it would not seek the death penalty.

Dressed in his camouflage Army fatigues, Manning sat at the defence table showing little expression.

A US military legal expert said the presiding officer is likely to make his recommendation on whether to court-martial Manning within eight days after the hearing ends. The hearing is expected to last over the weekend and possibly well into next week.

The site of the hearing, Fort Meade, is home to US Cyber Command, the organisation whose mission includes protecting computer networks like the one Manning allegedly breached by illegally downloading huge numbers of classified documents in Iraq.

Manning's lawyer said that the documents' release did little actual harm.