Bradley Manning, 24, has been in military custody since his arrest in Iraq more than two years ago on accusations that he leaked hundreds of thousands of confidential documents to the anti-secrecy website WikiLeaks.
He faces life imprisonment if he is convicted of the most serious charge that he "aided the enemy," but his defense team argues that the case should be thrown out because of Manning's unduly harsh treatment in jail.
The soldier, who broke his silence in the case on Thursday by testifying at a pre-trial hearing near the US capital, was being cross-examined by military prosecutors.
"Yes, sir," Manning said, after Major Ashden Fein showed him the sheet, which had been rolled up into a ligature with several knots tied along it. Both men referred to the bed sheet as a noose.
The soldier was considered a suicide risk when the bedding was taken from the cell where he was initially held at a US garrison in Kuwait. He was later transferred to Quantico brig in Virginia.
Manning's defense team maintains that he was kept isolated and under suicide watch despite objections from psychiatrists at Quantico and is demanding that the case be dismissed because of the alleged mistreatment.
The former army intelligence analyst, who was arrested near Baghdad in May 2010, repeatedly asked to be taken off the stringent suicide watch regime, but the request was refused despite the advice of military doctors.
On Thursday, Manning said that before his transfer to Quantico, guards in Kuwait repeatedly searched his cell and scattered his possessions, but a day later he told Fein that his initial treatment had been "very professional."
Fein also asked the soldier about his cell at Quantico, which consisted of three walls, a toilet, a sink and a row of bars.
Seated in a black, swivel chair in the courtroom, Manning appeared calm and relaxed as he conceded that the cell received natural light from a row of windows further down the hall and was the same as that of other detainees.
He also recounted some of the requests he made of military authorities, through the submission of paper chits, while held in custody.
Among them was a chit asking his aunt to send him a copy of "The Good Soldiers," a novel about the horror of modern combat written by Washington Post reporter David Finkel, and copies of the Scientific American journal.
Manning is accused of passing a mass of Iraq and Afghanistan war logs plus confidential diplomatic cables to WikiLeaks, which published them, causing deep embarrassment in Washington and enraging US allies around the world.
He is due to go on trial in February next year.