Lawyers for the Canadian say their client was tortured in Syria after the United States turned him over as an al-Qaida suspect.
They have called on Attorney General John Ashcroft and congressional intelligence committees to investigate, according to letters released on Tuesday.
Lawyers for Maher Arar, a Canadian citizen born in Syria, wrote to Ashcroft in a 10 November letter: "There is good reason to believe that the United States knew and wanted Arar tortured to obtain information.
"There is also no basis for the belief that Mr Arar has any connection to terrorism."
The lawyers asked Ashcroft to investigate whether there was any violation of a US law that prohibits sending a person to a country where it was believed the person would be tortured.
Arar was arrested in September 2002 while changing planes in New York on his way back to Canada from Tunisia. The 33-year-old telecommunications engineer was sent to Syria several days later, despite insisting he be flown home to Canada.
Canada is struggling to contain the fallout from the case of Arar, who was released last month and said he had been regularly tortured during the year he spent in Syria.
US authorities alleged he was a member of al Qaida and say they acted on data supplied by Canadian police.
Canadian critics are demanding a public inquiry into whether Canadian and US officials conspired to have Arar illegally deported to Syria so he could be tortured there.
Canadian Prime Minister Jean Chretien has criticised the United States for deporting Arar to Syria and said Ottawa asked Washington to investigate whether Canadian officials played any role in the case.
Lawyers for Arar also sent letters to US congressional intelligence committees calling for an investigation "into the extent to which the United States is condoning and aiding in torture."
There was no immediate comment from the Justice Department or congressional committees due to the federal Veterans Day holiday.
Senate Democratic Leader Tom Daschle of South Dakota said he believed the case deserved consideration and for Congress "to determine what the facts are and what response, if any, ought to be achieved on the part of our country as we look at these circumstances."