Supporters of the man charged with stealing 250,000 classified US documents published by WikiLeaks say the White House is trying to break the young soldier.

Private Bradley Manning has been held in a military prison for eight months.

His supporters have told the ABC's Four Corners program the US government is pressuring him to implicate WikiLeaks founder Julian Assange in the theft of the documents.

The Four Corners investigation has also discovered a fierce debate within WikiLeaks over whether it was in Manning's best interest to publish the cables.

Manning was charged with transferring information from military computers without authorisation, and could spend the next 50 years in prison.

He was turned in by former computer hacker Adrian Lamo, who befriended the young private.

Mr Lamo has revealed the contents of their online chats to Four Corners, saying Manning openly confessed to being a WikiLeaks source.

"For me, the precise moment at which I felt that what Bradley Manning was doing was a danger to national security and to the lives of others was when he characterised one of his leaks as being in excess of a quarter of a million State Department documents," he said.

To date, there is no evidence Mr Assange directly helped or conspired with Manning to take the classified material.

Supporters of Manning say his prison conditions are designed to break the 23-year-old and force him to implicate Assange.

One of the few civilians Manning is allowed to see is Boston researcher David House.

Mr House, who is a member of the private's legal advocacy team, alleges the conditions Manning is being held in at the Quantico military brig outside Washington amount to torture.

"From getting to know him and from watching his state degrade over time, the only conclusion I can reach is that this is torture," Mr House told Four Corners.

Mr House also alleges US federal agents investigating Manning's suspected connections with hackers in Boston have attempted to bribe members of the city's hacker community.

And he himself has been stopped at airports and had his computers seized, but without any charges being laid against him.

"It's almost thuggish behaviour on the part of the US government and the way they're prosecuting this investigation, and for someone who's doing legal defence, it's very alarming to see my country devolve into this," said Mr House.

Internal debate

Four Corners has also discovered a fierce debate within WikiLeaks over whether it was in Manning's best interest to publish the cables.

Former WikiLeaks insider Daniel Domscheit-Berg told the program he was "devastated" at the news of Manning's arrest and questioned the decision to release the cables in the first place.

"If the cables had not been published, there would've been no proof that anyone had given the material to a different entity," Mr Domscheit-Berg said.

"So from my perspective, what should have happened with these cables, for the sake of Bradley Manning, would have been to just keep them back as long as possible until you find out what is happening with him before you publish them.

"Because that's just feeding allegations of spreading material to other entities, and that might mean new charges that have not come up at this point in time."

For his part, Mr Assange maintains WikiLeaks does not know the identity of its sources.

"Because we don't know who our sources are, we cannot be in a position where upcoming publications can be affected by taking hostages ... that would be a very dangerous precedent to set. We have a promise to our sources that we will publish," he told Four Corners during an interview in England in January.

When asked about the internal debate over Manning, Mr Assange said:

"We were concerned as to how that would possibly play into his case and we saw that his charges only included some 50 cables, and so we were not sure whether that related to the material that we'd released," he said.

"But we could see that extra accusations would probably be made against him given that that he was the only name being floated around by the US military."

Mr Assange says the Guardian newspaper in England set out the exact timetable for the eventual publication of the cables, but told Four Corners: "It was very, very important to have them published eventually. The particular timetable was not of our choosing."

WikiLeaks has so far donated $15,000 to Manning's legal defence, but Mr Assange would not comment on what the organisation was doing now to support Manning.

"If the allegations against Bradley Manning are true, he is the United States' foremost political prisoner," he said.

Mr Assange is himself in the middle of a legal battle with Swedish authorities trying to extradite the WikiLeaks founder from the UK so he can be interviewed over complaints of sexual misconduct.

Giving his own view on Mr Assange and Manning's respective legal positions, Mr Domscheit-Berg told Four Corners:

"All this hype about WikiLeaks and Julian and Julian's problems in Sweden, what are these problems in Sweden compared to the trouble that this private is in?

"This person who potentially is, I think, one of the biggest heroes for freedom of information in our time, how does that relate? There's no relation in between these two things anymore.

"Everyone should be talking about Manning and not about Julian's trouble in Sweden or in Great Britain or wherever."

- Watch the full Four Corners program at 8:30pm on ABC 1.