EMILY BOURKE: But first, the American soldier responsible for the largest ever leak of secret US government and military documents has revealed what was going through his mind at the time of the leak.

US Army Private Bradley Manning has told a military tribunal he passed on secret files about the wars in Iraq and Afghanistan to WikiLeaks in order to spark a "public debate".

During the court hearings overnight. Private Manning pleaded guilty to 10 of the 22 charges against him. But he's denied the most serious allegation against him - aiding the enemy - and may still be prosecuted.

For the latest, I spoke to North America correspondent Jane Cowan.

Jane, which charges has Private Manning actually pleaded guilty to? What's he confessed to?

JANE COWAN: Well, Emily the 10 lesser charges relate to violations of military law. He's basically confessing though to providing vast archives of these military and diplomatic files to the WikiLeaks website. The charges that he's pleading guilty to include, for instance, the unauthorised possession and the wilful distribution of information - information that he accessed from a military database.

He's also admitted to the misuse of documents pertaining to Guantanamo Bay, also a memo from an unnamed intelligence agency and records from a military operation in Afghanistan.

But Emily, it doesn't really change the outlook for his case because he is still pleading not guilty to 12 other charges, including that most serious charge of aiding the enemy, which is a violation of the Espionage Act and that's the big one.

EMILY BOURKE: This is regarded as the largest ever leak of secret US government documents. What do we know now about Private Manning's motives?

JANE COWAN: Well, today Private Manning during this pre-trial proceeding read from a 35 page document and he did give some insight into his thinking. He said that he had wanted to start a domestic debate about the role of the military and foreign policy in general. He said that he wanted to make the world a better place and he also revealed that he initially considered giving this information to both the Washington Post newspaper and the New York Times, but ended up settling on WikiLeaks and said that afterwards he did feel that he had accomplished something that would allow him to have a clear conscience.

EMILY BOURKE: Well, Bradley Manning's already been behind bars for some time now. What are the prospects of him ever being a free man?

JANE COWAN: You're right, Em. He's been in custody since he was arrested in Iraq in May 2010 so that's almost three years now and Bradley Manning supporters just held vigils recently marking day 1000 of the 25-year-old's detention.

The aiding the enemy charge carries a life sentence and even the 10 charges he's admitting to do expose him to a sentence of 20 years combined so that's a long time behind bars no matter what happens.

Remember too, the military judge Colonel Denise Lind, last month decided to shave something like 112 days off any eventual sentence to compensate for the overly harsh treatment that she judged he had suffered while he was being held in detention at Quantico marine base but even that is a drop in the bucket you have to say when Private Manning is staring down life behind bars if he's convicted of that main charge.

EMILY BOURKE: Jane, what are the broad ramifications of what Private Manning has had to say overnight? Is there any bearing on the case against the WikiLeaks founder, Julian Assange?

JANE COWAN: Well, that is what's hanging over this entire case - the association with Julian Assange and what it might mean for him. There has been the suggestion from the start that the US might be interested in using the Manning case to gather information that could eventually be used in pursuit of Julian Assange.

Interestingly, Private Manning did make a point of saying today that no-one associated with WikiLeaks pressured him into sending any more information and that he takes full responsibility.

He did also say today that he struck up an online chat room relationship with someone who he said he assumed was a senior figure in the WikiLeaks group, someone like Julian Assange, whose name he actually mispronounced today in the hearing room as Assanjay (phonetic) and he also said that he came to greatly value his online conversations with the WikiLeaks person because he felt so isolated in Iraq.

But he didn't elaborate any further. He also, Emily, didn't say anything about his later online conversations with the former computer hacker, Adrian Lamo, who was the one remember who alerted the US government to the leaking but the court martial proper is set to begin in June so we'll find out more then.

EMILY BOURKE: North America correspondent Jane Cowan.