WASHINGTON — An international human rights watchdog is demanding that U.S. officials intervene to protect Canadian teenager Omar Khadr from torture at Guantanamo Bay.

The Inter-American Commission on Human Rights, affiliated with the Organization of American States, said Wednesday that Khadr faces an "urgent risk of irreparable harm.''

The commission's finding, after a one-day hearing last week, said American authorities must ensure Khadr, 19, isn't subjected to abuse, prolonged isolation or interrogation tactics that fail to comply with international standards of humane treatment.

The group demanded an impartial investigation into Khadr's torture allegations and prosecution of anyone found guilty. Officials must also ensure that no statements obtained through cruel or degrading treatment be accepted in legal proceedings against the teen, the commission said.

The watchdog gave the U.S. government 15 days to respond to its requests. So far, officials have refused to comply with five other urgent directives related to Guantanamo issued by the commission since March 2002.

U.S. officials have always denied detainees are tortured. Yet a Pentagon spokesman said Wednesday the department is considering whether to issue new instructions to military commissions that specifically prohibit evidence extracted by those means. "This has been one area where there has been some concern raised and so the department is taking a look at it and may issue a special instruction on it,'' said Bryan Whitman.

Sheku Sheikholeslami, part of an American University legal clinic that made the case to protect Khadr, said supporters are pleased with the commission's findings.

"It sends a very important message that the conditions of his detention will irreparably harm Omar,'' she said.

"This should be a wakeup call for the U.S. and especially for Canada,'' which has not taken a position on global calls to close Guantanamo.

Khadr is charged with murdering a U.S. army medic in Afghanistan in 2002 when he was 15 years old and faces a second military tribunal hearing next month at the U.S. naval base in southeastern Cuba.

Sheikholeslami argued at a closed-door March 13 hearing that Khadr's trial should be suspended. But the commission wants a full briefing on the tribunal process before ruling.

The U.S. Supreme Court is hearing arguments this month on whether the system for so-called enemy combatants captured in the war on terrorism is constitutional since they've been denied the right to challenge their detention.

Khadr's lawyers told the OAS commission that U.S. authorities aren't following global standards for juvenile justice, saying his trial sets a dangerous precedent as the first for war crimes allegedly committed by a juvenile.

The teen, they said, has been threatened with rape, placed in a room with barking dogs while wearing a plastic bag over his head and forced to sit while shackled in stress positions for extended periods.

U.S. government lawyers argued the commission has no jurisdiction over Guantanamo.

They also failed to provide any specifics about Khadr's case, citing privacy concerns, the commission said.

Only 10 of some 500 Guantanamo prisoners, including Khadr, have actually been charged and have made appearances at tribunals.

The Khadr family has provoked intense debate in Canada. Each of the five Khadr siblings, all of whom are Canadian citizens, has at one time or another been separately accused or investigated for alleged links to terrorism.