The Canadian government has sought an emergency stay of a judge's decision to give a former Guantanamo Bay inmate bail while he appeals his conviction for war crimes in the US.

The request comes in material filed late on Monday as part of a Canadian attempt to block Omar Khadr's release from prison, which could come as early as Tuesday evening.

The government said that granting bail to Khadr would threaten the entire system of international prisoner transfers.

Khadr's release could unsettle the system by "introducing uncertainty and a lack of control over the manner in which Canadian offenders' sentences are enforced", the government said in documents obtained by local media outlet, The Canadian Press.

Despite having presented no such evidence at his bail hearing, the government now argues that allowing Khadr out given his long imprisonment presents a risk that is contrary to the public interest.

"Springing (him) into the community rather than allowing him to continue his planned reintegration poses an undue risk,'' the government stated.

It does not elaborate on the nature of the risk but notes he has applied for parole in June.

In response, Khadr's lawyers said the government's case for a stay was weak.

'Knee-jerk' reaction

Khadr's legal team said, the government acknowledges Khadr's case is unique and will have little or no effect on other prison transfers.

"The onus is on the (Crown) to establish that irreparable harm will actually occur if a stay is not granted,'' they stated in their reply.

The last-ditch stay application, slated to be heard by a single Court of Appeal justice on Tuesday morning, says the government "will suffer irreparable harm'' if the Toronto-born Khadr, now 28, is released.

In a statement, a Khadr support group denounced the government's "unrelenting vilification'' of the prisoner and its "knee-jerk'' appeal of every court decision favourable to him.

"The rights, freedom and liberties of all Canadians are diminished by the actions of this government,'' Free Omar Khadr Now said.

Khadr returned to Canada from Guantanamo Bay in 2012 under the International Transfer of Offenders Act.

The Canadian was due to serve out his eight-year sentence for five war crimes committed in Afghanistan.

The US State Department said in a statement to CBC on Monday that releasing Khadr on bail would not strain Canada-US relations.

Khadr spent a decade at Guantanamo Bay, Cuba, and was handed an eight-year sentence by a US military commission in 2010 for the war-crime charges, including throwing a grenade when he was 15 years old that killed a US Army sergeant in 2002.

Khadr, now 28, agreed to a plea deal in 2010, but has since said he only pleaded guilty to get out of Guantanamo and be sent back to Canada.

Source: AP