A US military judge is set to rule Thursday if WikiLeaks suspect Bradley Manning can be charged with the serious crime of "aiding the enemy" for allegedly leaking classified documents to the website.

Manning's lawyers asked the judge at pre-trial hearings this week to dismiss the most grievous charge facing their client, arguing the government must drop the count unless it can prove the US Army private had the intention of helping Al-Qaeda when he allegedly passed files to WikiLeaks.

Otherwise, defense lawyers argue, the government's case implies any soldier could be prosecuted for espionage if they spilled secrets online or discussed sensitive information with news reporters.

Prosecutors counter that Manning's intent is not at issue and that the government only needed to prove that the intelligence analyst knew Al-Qaeda would see the leaked information on the anti-secrecy WikiLeaks site.

The 24-year-old Manning faces a possible life sentence if convicted on the aiding the enemy charge, known as article 104 in the military justice code.

At Wednesday's hearing, Manning's civilian counsel, David Coombs, insisted that under the government's interpretation, a soldier could be tried on the charge simply for telling a Washington Post reporter about high suicide rates, low morale or pervasive post-traumatic stress disorder in his unit without authorization.

As the courtroom fight underscored the legal dilemmas of a digital era, rights groups voiced alarm at the prosecution's tough line over online leaks.

"The implications of the government's argument are breathtaking," said Ben Wizner of the American Civil Liberties Union.

"In its zeal to throw the book at Manning, the government has so overreached that its 'success' would turn thousands of loyal soldiers into criminals," Wizner wrote on ACLU's website.

Manning is accused of leaking 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 a low-ranking intelligence analyst in Iraq.

The judge earlier on Thursday rejected defense motions asking for some of the other 22 counts to be tossed out or consolidated, after Manning's lawyers alleged the prosecution had "over-charged" their client.

Given the "volume of records" leaked, the counts were reasonable and prosecutors had not "piled on the charges" as the defense argued, said the judge, Colonel Denise Lind.

Manning, who appeared in court clad in a blue Army dress uniform, has yet to enter a plea in the case. His trial is due to begin on September 21.

Prosecutors said they only have to prove that Manning passed along the classified data and not whether the leak caused damage to national security.

The case does "not require the United States to prove actual harm" was done, said prosecutor Major Ashden Fein, who argued for a motion to exclude any discussion of the leak's effect.

Manning was transferred a year ago from a military prison at Quantico, Virginia -- where he had been imprisoned since July 2010 -- to another in Fort Leavenworth, Kansas.

During Manning's eight months of solitary confinement at Quantico, he was subjected to "cruel, inhumane and degrading treatment," according to a UN special rapporteur.

Manning is painted as a traitor for his alleged role in the worst ever breach of US intelligence, which embarrassed Washington and dismayed US allies.

But supporters of Manning, some of whom sat in the courtroom watching the proceedings this week wearing T-shirts inscribed with the word "Truth," view the soldier as a political prisoner and praise WikiLeaks for uncovering government secrets.

"Bradley Manning has now spent over 700 days in pre-trial confinement, in clear violation of his right to a speedy trial," said Kevin Zeese, a legal adviser from the Bradley Manning Support Network.

"Through their own incompetence -- whether deliberate or not -- the Pentagon's lawyers are only exacerbating an unjust persecution of a whistle-blower."