MONTREAL - The closing of the US "war on terror" prison at Guantanamo Bay, Cuba does not necessarily mean that detainee Omar Khadr will return to Canada, Prime Minister Stephen Harper said.

Khadr, who was captured in Afghanistan in 2002 at age 15, is the last Westerner held at the US naval base. His trial is due to open on January 26, six days after Barack Obama takes the oath of office as US president.

"The promise that president-elect Obama made was that he would close down the facilities at Guantanamo," Harper told reporters in the west coast city of Vancouver on Monday.

"That's primarily, as I understand it, because of the objection to the fact that many of the people at that facility aren't charged with anything."

He added: "I don't think you can necessarily leap to the conclusion that it will affect people who have in fact been charged, and who are facing a legal process. We don't know the answer to that question."

"We have a situation that's completely different with Omar Khadr. He has been accused of very serious matters. And there is a legal process that has to be taken," Harper said.

Opposition parties in Canada and human rights groups have been clamoring for Khadr to be repatriated to Canada where he would be treated as a former child soldier.

Khadr has been charged with killing a US soldier with a hand grenade. He also faces charges of material support for terrorism and espionage.

His father Ahmed Said Khadr, an Egyptian-born Canadian national, was a suspected Al-Qaeda leader who was killed in a gunbattle with Pakistani troops.

Obama, who takes office January 20, has vowed to close the controversial detention camp, which was created by the administration of President George W. Bush, and deal with its 250 remaining internees constitutionally.

Of the remaining inmates, only some 20 have been charged, including five men accused of helping organize the September 11 attacks of 2001.