The United Nations has appealed to the US to stop the military trial of Canadian Omar Khadr, who is being held at Guantanamo Bay since 2002 and was 15 when he allegedly threw a grenade that killed a US soldier in Afghanistan.
Khadr's trial begins today at Guantanamo Bay.
Radhika Coomaraswamy, a senior UN official on child protection, said that the continuation of this trial would set a very dangerous precedent for children worldwide.
"Since World War II, no child has been prosecuted for a war crime," she said.
"Child soldiers must be treated primarily as victims and alternative procedures should be in place aimed at rehabilitation or restorative justice."
Coomaraswamy said that the statute of the International Criminal Court specifies that no one under the age of 18 could be tried for war crimes.
Khadr, now 23, is the youngest of the 176 prisoners still held at the naval base.
His trial is the first full case to be heard by the military commission during the Obama administration.
Human rights organisations have blasted both the Canadian and US governments for going ahead with the trial of a juvenile in a military court.
According to activists, the Canadian government has not pushed Washington to send Khadr back to his home country for trial or asked that he be tried in a regular US court, which will give him a higher degree of protection.
"The Canadian government with breathtaking defiance has refused...to lift a single finger to ensure that something is done to protect his rights," Alex Neve, Secretary General of Amnesty International, Canada, told CNN.
"We are not going to give up at all," Neve added.
"We have been speaking out about Omar Khadr's situation and demanding that his rights be protected for eight years now and we will continue for as long as it takes."
Coomaraswamy noted that the US and Canada had played a vital role in the creation of mechanisms within the UN to protect the rights of children, which had secured the release thousands of child soldiers around the world.
The UN official urged the governments not to ignore the rights of children, which applied in this case.
"I urge both governments to come to a mutually-acceptable solution on the future of Omar Khadr that would prevent him from being convicted of a war crime that he allegedly committed when he was child," she said.