The defense was summing up its case on Friday in the court martial of Bradley Manning, the US army private who sent hundreds of thousands of US government documents to the anti-secrecy group WikiLeaks.

Manning's civilian defense attorney David Coombs was giving his closing argument in the eighth week of the trial at the Fort Meade army base outside Baltimore. The case will then go to the judge for deliberations, who has said she could rule anytime in the next several days.

"Tomorrow, you're going to hear what truth sounds like," Coombs told supporters Thursday night after a lengthy and bruising final argument by the prosecution.

Speaking for more than five hours Thursday, with several breaks through the day for people to use the bathrooms and eat lunch, Major Ashden Fein told the court Manning was a traitor with one mission as an intelligence analyst deployed in Iraq in 2009 and 2010: to find and reveal government secrets to a group of anarchists, then bask in the glory as a whistleblower.

"The government has its job, but there is nobody who could believe what they said – much less them," Coombs told a group of 40 supporters after Thursday's session.

"If it takes six, seven hours to go on a diatribe and try to piece together some convoluted story … if it takes you that long to get your point across, you know it isn't true," Coombs told supporters in the courtyard of the court building as they were leaving for the day.

He said his closing arguments would likely last about two hours Friday and that he is "going to speak from the heart – it won't be hard for me to rebut."

Coombs has said the soldier was troubled by what he saw in the war – and at the same time was struggling as a gay man in the era of "don't ask don't tell". Those struggles made him want to do something to make a difference and he hoped revealing what was going on in the war zone and US diplomacy would inspire debate and reform in American foreign and military policy, Coombs has said.

Fein said Manning betrayed his country's trust and spilled classified information, knowing the material would be seen by the terrorist group al-Qaida.

"WikiLeaks was merely the platform which Pfc Manning used to ensure all the information was available for the world, including enemies of the United States," Fein said.

Manning, 25, is charged with 21 offenses, but the most serious is aiding the enemy, which carries a possible sentence of up to life in prison. A native of Crescent, Okla., Manning has acknowledged giving WikiLeaks 700,000 battlefield reports, diplomatic cables and videos. But he says he didn't believe the information would harm troops in Afghanistan and Iraq or threaten national security.

A military judge, not a jury, is hearing the case at Manning's request. Army colonel Denise Lind will deliberate after closing arguments.

The verdict and any sentence will be reviewed, and could be reduced, by the commander of the Military District of Washington, currently Major General Jeffery S Buchanan.