Preliminary talks have been held to end Omar Khadr’s war-crimes trial with a plea bargain that could lead to his release and repatriation to Canada, but agreement from the Canadian government would be critical to any final deal, Mr. Khadr’s lawyers said.

There have been conversations in recent days and further talks are possible, said Barry Coburn, lead civilian attorney for Mr. Khadr, the only Canadian facing war crimes and terrorism charges under the U.S. government’s revised but still controversial military tribunals at Guantanamo Bay.

However, prosecutors seeking to convict Mr. Khadr on murder and terrorism charges refused to confirm plea-bargain talks. “Mr. Coburn may have greater latitude to talk about that issue,” said U.S. Navy Captain David Iglesias, spokesman for the prosecution. “I absolutely cannot talk about whether or not there are ongoing discussions.”

Mr. Khadr is due to appear Wednesday in the heavily guarded courtroom for pretrial motions. His defence team will seek to have his confessions ruled inadmissible because they were extracted by torture from Mr. Khadr, who was gravely wounded and 15 years old at the time, his lawyers say.

Unlike Britain and Australia, which demanded the return of their citizens held in Guantanamo, successive Canadian governments have rejected calls to bring Mr. Khadr home.

But any plea-bargain deal would necessarily involve Canada, along with Mr. Khadr, the prosecution and the U.S. government.

Mr. Coburn said the defence team hadn’t had direct talks with the Canadian government but added: “It’s not necessarily us who would be approaching Canada.”

Although there have been persistent reports that senior Obama officials – like Bush officials before them – have approached the Canadian government about resolving the Khadr case, Canada has never shown any interest.

“We all expected a lot more from the Obama administration,” said Alex Neve, secretary-general of Amnesty International Canada, who is in Guantanamo as part of a small group of international rights observers.

Mr. Neve called Prime Minister Stephen Harper’s steadfast refusal to seek Mr. Khadr’s repatriation a “deep national disgrace.”

No real precedent exists in the murky military tribunals that U.S. President Barack Obama has maintained, even though they were widely discredited and repeatedly ruled as unconstitutional during the administration of George W. Bush.

But Michael Berrigan, the senior chief defence counsel, said a deal can be worked out even if the tribunals are proceeding with a manual that was only finished Tuesday night.

“Like most things in Guantanamo, they can make it up as they go along,” Mr. Berrigan said.

Talk of a plea deal may reflect an effort to force both the Obama administration and the Harper government to deal with the fact that the trial of what many rights activists consider a child soldier is looming with fallout for both leaders.

The closest analogy to Mr. Khadr’s case – and the sole previous plea bargain of a Guantanamo detainee – was the spring of 2007 pact in which David Hicks, the so-called “Australian Taliban,” was flown home after agreeing to plead guilty to a single charge of material support for terrorism.

Mr. Hicks, who had spent six years in Guantanamo at the time of the deal, spent nine months in prison in Australia before being freed.

However, Mr. Khadr, accused of murder because he is alleged to have been an unlawful combatant who tossed a grenade that killed a U.S. special forces medic in the summer of 2002, faces a different political landscape.

Mr. Hicks had considerable public support in Australia and then prime minister John Howard was under political pressure to act on behalf of a citizen.

Mr. Khadr, one of several sons of Ahmed Said Khadr, a senior al-Qaeda figure, has stirred little support among Canadians, many of whom regard the family as citizens of convenience.