Khadr was captured in Afghanistan in 2002 when he was 15 years old. He is accused of throwing a grenade that killed U.S. Army soldier Christopher Speers and has been detained since 2002 at the U.S. naval detention facility at Guantanamo Bay, Cuba.
In a plea deal, Khadr is expected to serve around eight years in prison when he is transferred to Canadian custody. He pleaded guilty Monday to several charges, including terrorism, as part of the plea deal.
Jo Becker, a children's rights advocate at Human Rights Watch, said Washington should consider Khadr's age during the sentencing phase.
Becker said the U.S. Supreme Court has ruled repeatedly that adolescents should get different treatment under the rule of law than adults.
"The U.S. treatment of Omar Khadr has been at odds with international standards on juvenile justice and child soldiers from the very beginning," said Becker in a statement. "As the military jurors consider sentencing this week, they need to take Khadr's status as a child offender into account."
Human Rights Watch said that with the sentencing, the United States becomes the first Western nation since World War II to convict a child in a war crimes tribunal.