Omar Khadr, seen before his arrest in 2002, has been held in the U.S. prison at Guantanamo Bay, Cuba, for five years. ((Canadian Press))

The U.S. Defence Department is appealing a judge's decision to drop all charges against Omar Khadr, the only Canadian detained in an American prison in Guantanamo Bay, Cuba.

Bryan Whitman, a spokesman for the Pentagon in Washington, said Friday his department wants military judges in Guantanamo to reconsider, because the ruling was largely based on a technicality.

A military judge on Monday dropped the charges of murder and terrorism because Khadr was officially classified as an "enemy combatant," but the military courts in Guantanamo only have jurisdiction to try "unlawful enemy combatants."

Khadr, 20, received his classification from a military panel in 2004, two years after he was captured in Afghanistan at the age of 15 and imprisoned in Guantanamo, where he has been held ever since.

"There is no material difference between the term 'enemy combatant' used by the combatant status review tribunal process and the term 'unlawful enemy combatant' as utilized in the Military Commissions Act, as it pertains to the individuals in question," Whitman said.

The Pentagon will file its appeal before the end of the day Friday, he said.

The Pentagon is also appealing the decision to overturn the charges faced by another Guantanamo prisoner — Salmi Ahmed Hamdan of Yemen. Hamdan's charges were dropped for reasons similar to those in Khadr's case.

Khadraccused of killing U.S. military medic

Khadr was accused of throwing a grenade that killed an American medic, Sgt. First Class Christopher Speer.

Khadr was arrested in July 2002 during a firefight with American troops in Afghanistan that left the teenager badly injured, with two gunshot wounds to the chest.

He was held inAfghanistan for three months and then transferred to Cuba.

Khadr, who was born in the Toronto area, spent several years of his childhood in Pakistan and Afghanistan. His family are reputed to be al-Qaeda sympathizers.

Hamdan, charged with conspiring to harm U.S. citizens, has admitted to being a driver for Osama bin Laden but denied taking part in the Sept. 11, 2001, attacks against the United States.

With files from the Associated Press