BRADLEY MANNING, THE young soldier accused of aiding the enemy by slipping a trove of national security secrets to WikiLeaks, sat quietly at the opening session of his pretrial hearing today as government and defense lawyers tangled over whether the presiding officer could be impartial.

Manning’s civilian defense lawyer argued that the presiding officer, Paul Almanza, an Army Reserve lieutenant colonel, is biased and should step aside, but Almanza refused. Almanza also denied a move by Manning defense to suspend the hearing while seeking to appeal Almanza’s decision to continue on the case.

The hearing is to determine whether Manning will face a court-martial on charges that he aided the enemy by leaking hundreds of thousands of classified military and diplomatic documents.

Almanza is a Justice Department prosecutor in civilian life, and Manning’s lawyer said that was reason enough to step aside. The Justice Department is conducting a criminal investigation targeting WikiLeaks founder Julian Assange.

After Almanza denied the request that he step aside, Manning’s lawyers said they would seek to appeal that decision to the Army Court of Criminal Appeals. It was unclear when the court would decide whether to hear the appeal.

Before that dispute, Manning, who turns 24 on Saturday, took notes during at his hearing at this Army base between Washington and Baltimore. Dressed in Army camouflage fatigues and wearing dark-rimmed glasses, Manning sometimes twirled a pen in his fingers as the hearing got off to a slow start.

A U.S. military legal expert told reporters shortly before the proceedings began that Almanza was likely to make his recommendation on whether to court-martial Manning within eight days after the hearing ends. The hearing is expected to last through the weekend and possibly well into next week.

The Manning case has spawned an international support network of people who believe the U.S. government has gone too far in seeking to punish the young soldier.

Manning’s supporters planned to maintain a vigil during the hearing and were organising a rally for Saturday. By midday today, about 50 protesters had assembled outside the military base’s main entrance, and a few dozen marched down an adjoining road carrying orange signs that read, “The Bradley Manning Support Network.”

A U.S. grand jury is weighing whether to indict Assange on espionage charges, and WikiLeaks is straining under an American financial embargo.

The materials Manning is accused of leaking include hundreds of thousands of sensitive items: Iraq and Afghanistan war logs, State Department cables and a classified military video of a 2007 American helicopter attack in Iraq that killed 11 men, including a Reuters news photographer and his driver.

At the time, Manning, a native of Crescent, Oklahoma was a low-level intelligence analyst in Baghdad.

Manning was detained in Iraq in May 2010 and moved to a Marine Corps brig at Quantico, Va., in July. Nine months later, the Army sent him to the military prison at Fort Leavenworth, Kan., after a series of claims by Manning of unlawful pretrial punishment.

When it filed formal charges against Manning in March 2011, the Army accused him of using unauthorised software on government computers to extract classified information, illegally download it and transmit the data for public release by what the Army termed “the enemy.”

The first large publication of the documents by WikiLeaks in July 2010, some 77,000 military records on the war in Afghanistan, made global headlines. But the material provided only limited revelations, including unreported incidents of Afghan civilian killings as well as covert operations against Taliban figures.

In October 2010, WikiLeaks published a batch of nearly 400,000 documents that dated from early 2004 to 1 Jan 2010. They were written mostly by low-ranking officers in the field cataloging thousands of battles with insurgents and roadside bomb attacks, plus equipment failures and shootings by civilian contractors.

A month later, WikiLeaks released hundreds of thousands of State Department documents, including candid comments from world leaders.