"Allah willing, we'll get a good number of Americans," an adult tutor is heard saying in Arabic, according to the subtitled translation on the video.

The video was found in a tunnel under the mud-walled compound where Khadr was captured in Afghanistan in July 2002, when he was 15 years old. He is now 23 and has spent a third of his life locked behind the razor wire at Guantanamo Bay, Cuba.

Defense lawyers want the video barred from court, alleging the military found it a month after Khadr's capture using information he gave during interrogations laced with torture.

It was the second time the court has seen the video, which prosecutors want to use as evidence in Khadr's July trial on charges of murdering a US soldier with a grenade during a firefight in Afghanistan, conspiring with Al-Qaeda and targeting US forces with roadside bombs.

The first showing came just before President Barack Obama took office in January 2009 and froze the tribunals at the US naval base at Guantanamo that he had called unfair. The tribunals are back in operation with a few new restrictions on hearsay and coerced evidence.

First up on Obama's watch is the trial of Toronto-born Khadr, whose father allegedly apprenticed him to Al-Qaeda bomb makers. It would be the first US war crimes tribunal to prosecute someone for acts allegedly committed as a minor.

The video shows Khadr smiling and sitting on a carpet assembling detonators in front of a stack of Russian-made anti-tank mines, apparently under the tutelage of the two bearded men seen with him. In footage shot with a night-vision camera, Khadr is seen with adult men who are burying the explosives in a road.

The argument over whether the video can be used as evidence was stalled by debate over whether Khadr had to wear blackout goggles and noise-blocking earphones as guards drove him from the detention camp to the hilltop courthouse at the US naval base in southeast Cuba.

His lawyers said the goggles pressed painfully against Khadr's eyes, aggravating the shrapnel embedded in both during the fight that led to his capture. He is blind in the left eye and has bullet wounds in his chest and shoulder from the battle.

A military lawyer who saw Khadr early Thursday quoted him as saying the goggles were imposed only "to humiliate me." Khadr skipped court in the morning and sat through the afternoon session with his hands over his eyes, dabbing at them with a tissue and crying occasionally.

Defense attorneys said he was in "extreme physical pain" that impaired his ability to assist in his defense.

A military spokesman said the goggles and earphones were a standard protection to keep detainees from learning the routes, attacking guards or hearing conversations during the 20-minute drive. He said doctors would examine Khadr on Thursday night and Friday.

FBI agent Robert Fuller, who interviewed Khadr seven times in Afghanistan shortly after his capture, said Khadr described feeling "happy" about planting the mines and sleeping with an unloaded AK-47.

"He mentioned he was proud to be a soldier," Fuller said.

He said Khadr chatted freely with FBI agents and told them his father collected donations from wealthy Canadians and funneled it through a charity that funded legitimate schools and orphanages along with Al-Qaeda guest houses and training camps in Afghanistan.

His father, Ahmed Said Khadr, moved his family frequently between Canada, Pakistan and Afghanistan and was killed in a shootout with Pakistani security forces in 2003.

Khadr described him to the FBI agents as a respected member of Osama Bin Laden's inner circle and helpfully identified photos of senior Al-Qaeda leaders his father had met with, Fuller testified.