US army solider Bradley Manning could face 136 years in prison for leaking military documents to whistleblower organisation WikiLeaks – as his sentencing hearing starts.
More than 20 witnesses are expected to be called for the hearing, which could last until 23 August.
They include experts on counter-intelligence, strategic planning and terrorism – both from the prosecution and defence.
The government said as many as half of the prosecution witnesses will testify about classified matters in closed court.
Manning was found guilty on Tuesday of 20 of 22 charges, including espionage and theft, but not the most serious charge he faced – “aiding the enemy”.
Lawyers for Manning are seeking to reduce his potential sentence by having some of his convictions merged.
The motions were revealed as the sentencing phase of Manning’s court-martial began on Wednesday at Fort Meade.
The motions seek to merge two of the six espionage counts and two of the five theft counts for which Manning was convicted.
All of the counts involve Manning’s leak of Afghanistan and Iraq battlefield reports.
If the judge agrees to merge the counts, it would mean Mr Manning faces up to 116 years in prison instead of 136 years.
Manning admitted sending more than 470,000 Iraq and Afghanistan battlefield reports, 250,000 State Department diplomatic cables and other material, including several battlefield video clips, to WikiLeaks while in Iraq in early 2010.
WikiLeaks published most of the material online. The video included footage of a 2007 US Apache helicopter attack in Baghdad that killed at least nine men, including a Reuters news photographer and his driver.
Manning said he sent the material to expose war crimes and deceitful diplomacy.
Meanwhile Wikileaks founder Julian Assange said the conviction sets a “dangerous precedent”. He added: “This was never a fair trial.”
He criticised the treatment of the US soldier since his arrest in 2010, saying he had been stripped, kept isolated and in a cage to “break” him.
Mr Assange said there were two appeals within the US justice system as well as the supreme court. “WikiLeaks will not rest until he is free,” he added.
Asked about the role of his whistleblowing website in the Manning case, Mr Assange said: “We are pleased that throughout this case no evidence was produced from WikiLeaks against Bradley Manning.
“The allegation against him is that he spoke to a US informer who turned him in. Our processes have been successful.
“It is of great concern to us to see any national security source victimised, but we have chosen not to enter into a debate over whether he is one of our sources.”
Mr Assange said he expected Manning to appeal against the decision.