Legal proceedings against Canadian Omar Khadr have been thrown into fresh uncertainty after the head of the U.S. military commission process at Guantanamo Bay, Cuba, secretly withdrew, then reissued charges against all defendants, Khadr's military defence lawyer said Tuesday.

The procedure — referred to as "withdrawal and re-referral" — has the legal effect of nullifying all prior proceedings in Khadr's case, Lt.-Cmdr. William Kuebler said in a statement.

"As of today, there is no trial date in the military commission case of Omar Khadr," Kuebler said.

He said documents recently disclosed by the U.S. Defence Department show that Susan Crawford, the Pentagon's top official for the military commissions, withdrew all charges on Dec. 17 and refiled them last Friday.

Kuebler said the latest "circus-like" proceedings could be a calculated ploy to pre-empt the incoming administration of president-elect Barack Obama, who has pledged to close the detention centre and shut down the controversial military commission process. Obama has said he wants those charged in the commission process to face trial in U.S. civilian courts.

"Whether the secret withdrawal of charges was part of a calculated effort to tie the hands of the new administration, it is abundantly clear that officials overseeing the military commission process are going 'all out' to make it as difficult as possible for President Obama to follow through on his commitment to end the sham military commission proceedings in Guantanamo," Kuebler said.

Khadr only Western citizen still at Guantanamo

Khadr's lawyer said military defence teams for "high-valued detainees" have speculated the move is really directed toward getting Khalid Sheikh Mohammed and other alleged conspirators in the Sept. 11, 2001, hijackings to plead guilty to military commission charges before Obama takes office.

Last month, Mohammed and four co-defendants attempted to confess and plead guilty to all charges against them, but their request was delayed pending mental evaluations of three of the accused.

Kuebler also noted that Crawford's December directive withdrawing charges calls for a new arraignment date on Martin Luther King Day, the day before Obama's inauguration on Jan. 20.

Khadr's military trial was set to begin six days after Obama is to take office.

Khadr, now 22, has been held at the U.S. navy base since shortly after his arrest in 2002 at age 15 on suspicion of killing a U.S. medic in Afghanistan.

A wounded Khadr was taken into custody after an hours-long firefight near the Pakistani border for allegedly lobbing the grenade that killed U.S. army medic Sgt. Christopher Speer.

He is the only Western citizen still imprisoned at the detention facility at Guantanamo, which was set up following the Sept. 11, 2001, hijackings.

Prime Minister Stephen Harper has remained firm in his position not to intervene in Khadr's case, saying a judicial process is underway.