U.S. embassies around the world are warning allies that WikiLeaks might be poised to release classified cables that could negatively impact relations by revealing sensitive assessments and exposing U.S. sources, a State Department spokesman said Thursday.

The State Department has prepared for the possible release - which WikiLeaks has said would be seven times larger than the Iraq files released last month - by reviewing thousands of diplomatic cables and "assessing the potential consequences of the public release of these documents," spokesman P.J. Crowley said.

Crowley said State does not know "exactly what WikiLeaks has or what they plan to do," but the consequences to American interests could be severe. The cables, for instance, could reveal that senior government officials in other countries are the sources of embarrassing information about the inner workings of those governments, thus making it more difficult for the State Department to obtain such intelligence in the future.

"Without getting into specifics, typical cables describe summaries of meetings, analysis of events in other countries and records of confidential conversations with officials of other governments and with members of civil society," Crowley said. "They are classified for a very good reason. They contain sensitive information and reveal sources of information that impact our national interests and those of other countries."

Crowley added that "the lives of people who provide us valuable information and perspective are being put at risk. They help us understand what is happening around the world and inform our policies and actions."

WikiLeaks has bedeviled the Obama administration with a series of damaging revelations about U.S. policy overseas. In July, it released more than 70,000 military reports on the war in Afghanistan and in October nearly 400,000 reports on the Iraq war. "Next release is 7 [times] the size of the Iraq War Logs," WikiLeaks stated in a posting on its Twitter page Nov. 21.

WikiLeaks has not disclosed the source of the materials. But suspicion has centered on Pfc. Bradley Manning, 22, an Army intelligence analyst whom the military arrested this year, charging him with the downloading and transfer of classified material.

In the past, WikiLeaks has provided a small group of news organizations with an advance peek at the information, with an understanding that their reports would be released simultaneously at a pre-agreed time. The Washington Post has never been part of such an arrangement with WikiLeaks.

WikiLeaks was founded in 2006 by a former computer hacker, Julian Assange. The organization has been under stress in recent months, with several members quitting, citing differences with Assange and the direction of the group. Assange is facing allegations in Sweden of rape and sexual harassment, which he has denied, saying the charges are part of a U.S.-orchestrated smear campaign.

The cables could also show that allies sometimes take private actions that directly contradict publicly declared policies. The London-based daily al-Hayat reported that WikiLeaks is planning to release files that show Turkey has helped al-Qaeda in Iraq - and that the United States has helped the PKK, a Kurdish rebel organization. The documents reportedly suggest that the U.S. has supported the PKK, which has been waging a separatist war against Turkey since 1984 and has been classified by the State Department as a terrorist organization since 1979.

News reports from around the globe indicate that foreign governments are bracing for the impact of the revelations.

U.S. ambassador to Canada David Jacobson has already phoned Minister of Foreign Affairs Lawrence Cannon to inform him of the matter, the Foreign Affairs department told the Canadian Press. Foreign Affairs spokeswoman Melissa Lantsman said the Canadian Embassy in Washington is "currently engaging" with the U.S. State Department on the matter.

In Australia, the Department of Foreign Affairs and other agencies in Canberra, including the Department of Prime Minister and Cabinet, met to discuss the leaks, which a senior Australian government official said had prompted a "strong measure of concern," according to the Australian newspaper. "The whole thing is pretty big," the official said.

"We condemn what WikiLeaks is doing," Crowley said. "Its actions are gratuitous, harm relations among countries and erode the trust that enables governments to cooperate and collaborate and work together to resolve regional and global challenges. Little good will come from what WikiLeaks has indicated it plans to do."