GUANTANAMO BAY, Cuba - The judge presiding over Omar Khadr's war-crimes case cleared the way for the trial to proceed by ruling on Monday that confessions the Canadian made can be used as evidence against him.

In making the ruling, Col. Patrick Parrish rejected defence arguments that Khadr's most damning statements were the product of torture.

"The motion to suppress the accused's statements is denied," Parrish said without giving reasons.

The judge also decided a prosecution video showing a teenage Khadr making and laying explosive devices in Afghanistan could be entered as evidence.

The rulings end months of bitter wrangling between defence and prosecution over the confessions and set the stage for the first war-crimes trial under U.S. President Barack Obama.

They come after Khadr's lawyer formally entered not-guilty pleas on all charges.

Jury selection is slated to start Tuesday morning, with opening statements expected Wednesday.

The Toronto-born Khadr, 23, faces five war-crimes charges, including killing an American special forces soldier by throwing a hand grenade in Afghanistan in July 2002 when he was 15 years old.

He was taken to Bagram prison in Afghanistan before being transferred in October 2002 to Guantanamo Bay, where he has been held since.

During Monday's hearings, Khadr sat beside his Canadian lawyer, Dennis Edney, reading a World Cup soccer magazine.

Edney called Parrish's rulings "disgraceful."

"If there are any doubts about the fairness of this proceeding, then this judge showed his true colours."

Dressed in white, the uniform of the most compliant prisoners, Khadr appeared relaxed and smiling at times.

Khadr had earlier threatened to boycott the hearings.

Edney cited the detainee responding to Parrish's rulings as saying, "we're just embarrassing ourselves by being here."

Earlier Monday, Khadr's Pentagon-appointed lawyer Lt. Col. Jon Jackson noted an interrogator had testified to telling Khadr how a young detainee in American custody had been raped by other inmates, possibly to death.

The incident involving former U.S. Army sergeant Joshua Claus occurred at Bagram prison soon after American forces captured the badly wounded Khadr eight years ago.

"He was 15 years old when Interrogator 1 (Claus) told him that story," Jackson said.

"Once he said those words ... the well is poisoned. The government can't cleanse the well."

Claus was later convicted of detainee abuse.

"By the time he left Bagram, he was broken ... because of the actions of people in uniform," Jackson said.

The prosecution branded as lies Khadr's assertions of abuse, noting he refused to take the stand to be cross-examined on the claims.

Capt. Chris Eason told Parrish that Khadr's confessions were freely given, reliable, and go to the heart of the case against him.

"He talked about the grenade. He talked about how he threw the grenade," Eason said.

"It's truth that we can rely on."

Khadr later recanted his statements only because other detainees were picking on him for co-operating with authorities, Eason said.

Jo Becker, of New York-based Human Rights Watch, called Parrish's ruling a "shame" in light of the rape and other threats against Khadr.

"This is a terrible precedent," Becker said.

"The first trial to go forward under the Obama administration is a former child soldier."

In other pretrial motions, Parrish ruled that security arrangements were fine despite a defence request for less obtrusive measures.

Parrish did rule out parts of a video that show the worst scenes of carnage from the 9/11 terrorist attacks on the United States.

He said those scenes would "not be helpful" to the jury.