Prosecutors must prove that US Army private Bradley Manning intended to help Al-Qaeda by passing secret government documents to the WikiLeaks website, defense lawyers argued Monday.

Manning's civilian attorney questioned the heart of the government's case against his client at a pre-trial hearing, contending that prosecutors had to show more than mere "negligence" to win a conviction for the serious offense of "aiding the enemy."

The government had to prove that Manning "intended to engage the enemy" by allegedly leaking sensitive files to a website, David Coombs said at the hearing at Fort Meade, northeast of Washington.

Otherwise the trial would ignore the realities of the Internet era and anyone who passed classified information to a newspaper could be accused of treason merely because adversaries have access to the web, he said.

Citing a hypothetical example, Coombs asked how the court would rule if someone passed information to the New York Times.

"The enemy can read the New York Times like anyone else," he said. "Have I now given information to the enemy?"

After defense lawyers and prosecutors sparred over the issue, Judge Denise Lind said she would draft instructions to a future jury that would take into account arguments from both sides.

Manning, 24, could spend the rest of his life in prison if convicted of aiding the enemy by handing hundreds of thousands of classified documents -- including military logs from Iraq and Afghanistan and State Department diplomatic cables -- to the WikiLeaks website.

He has not yet entered a plea in the court-martial, which is tentatively due to start in September.

Prosecutors maintain they only have to prove that Manning knew Al-Qaeda might see the sensitive intelligence files posted by WikiLeaks, given his training as a military intelligence analyst.

Captain Joe Morrow, one of five prosecutors in the case, said the government is asserting that Manning had "knowledge of a very definite place" when he allegedly handed over a trove of files, a reference to the WikiLeaks website.

But the defense argues the government has to demonstrate the army private "knowingly and intentionally gave intelligence to the enemy," according to a defense motion filed before the hearing.

"Today everyone understands that information posted on a publicly accessible website can potentially be viewed by anyone with Internet access," the motion said.

The massive document dump to WikiLeaks triggered a diplomatic firestorm that embarrassed US officials and rankled allies, but Manning's supporters say he has shed light on secretive decision-making in Washington and other capitals.

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.

The case has highlighted difficult legal questions raised by new technology, with the court struggling to apply laws that that have failed to keep pace with digital advances.

At Monday's hearing, the first of a five-day round scheduled this week, Manning's lawyer also argued that his client had permission to download secret diplomatic cables and should not be charged with an electronic "break-in" of government networks.

Coombs asked for the dismissal of two counts against his client, saying that Manning did not steal a password or otherwise hack into a government computer network when he downloaded classified State Department cables.

Accusing prosecutors of failing to recognize "uncomfortable facts," Coombs said Manning was free to access the diplomatic cables and never circumvented any "electronic gate" when he downloaded the files.

But the prosecution said the "Wget" software he used, which is designed to retrieve computer files quickly, was not authorized and that Manning's actions therefore amounted to a "trespass."

Coombs acknowledged that Manning could be charged with a lesser offense for using the software, which he said was akin to a worker violating contractual terms set down by a company for computer use.