OTTAWA - The U.S. government has notified Ottawa that the WikiLeaks website is preparing to release sensitive U.S. diplomatic files that could damage American relations with allies around the world.

U.S. officials say the documents may contain accounts of compromising conversations with political dissidents and friendly politicians as well as activities that could result in the expulsion of U.S. diplomats from foreign postings.

U.S. Ambassador to Canada David Jacobson phoned Minister of Foreign Affairs Lawrence Cannon to inform him of the matter, a foreign affairs spokeswoman said Wednesday.

Melissa Lantsman said the Canadian Embassy in Washington is "currently engaging" with the State Department on this matter.

"We are not privy to the full contents of documents which may be leaked," Lantsman said in an email to The Canadian Press.

A State Department spokesman said Wednesday the release of confidential communications about foreign governments probably will erode trust in the United States as a diplomatic partner.

"These revelations are harmful to the United States and our interests," state department spokesman P.J. Crowley said. "They are going to create tension in relationships between our diplomats and our friends around the world."

U.S. diplomatic outposts around the world have begun notifying other governments that WikiLeaks, a group that bills itself as a website devoted to reforming governments worldwide by exposing their secrets, may release these documents in the next few days.

Many of the cables are believed to date from the start of U.S. President Barack Obama's administration, meaning that the White House will not be able to distance itself from any disclosures.

One concern, for example, is that the documents may reveal the kinds of pressure the U.S. administration has put on various countries to accept the transfer of Guantanamo Bay detainees who have been cleared for release but are unwelcome in their home countries.

Canadian detainee Omar Khadr was the subject of discussions last month between Cannon and U.S. Secretary of State Hillary Clinton.

Canada has long resisted repatriating Khadr, the only western detainee remaining at Guantanamo Bay, despite pressure from both American and Canada's federal courts. That position is thought to have caused tensions between the two countries.

The Toronto-born Khadr pleaded guilty last month to five war crimes, including the murder of a U.S. soldier during a firefight in Afghanistan in July 2002.

On Oct. 31, Khadr was sentenced to eight years in prison. According to a pre-trial deal, the 24-year-old man will serve one more year in U.S. custody, and after that he can apply to transfer to Canada to serve out the balance of his sentence under Canadian terms.

It remains to be seen if diplomatic cables between Ottawa and Washington regarding Khadr, the Canadian mission in Afghanistan or other bilateral matters will be among the documents expected to be released this weekend.

--With files from the Associated Press.