WASHINGTON (Reuters) - Classified U.S. diplomatic cables reporting corruption allegations against foreign governments and leaders are expected in official documents that WikiLeaks plans to release soon, sources said on Wednesday.

A man carries a briefcase in a file photo. REUTERS/File

The whistle-blowing website said on its Twitter feed this week its next release would be seven times larger than the collection of roughly 400,000 Pentagon reports related to the Iraq war which it made public in October.

Three sources familiar with the State Department cables held by WikiLeaks say the corruption allegations in them are major enough to cause serious embarrassment for foreign governments and politicians named in them.

They said the release was expected next week, but could come earlier.

The detailed, candid reporting by U.S. diplomats also may create foreign policy complications for the administration of U.S. President Barack Obama, the sources said.

Among the countries whose politicians feature in the reports are Russia, Afghanistan and former Soviet republics in Central Asia. But other reports also detail potentially embarrassing allegations reported to Washington from U.S. diplomats in other regions including East Asia and Europe, one of the sources familiar with the WikiLeaks holdings said.

The U.S. government has strongly objected to past WikiLeaks revelations, which it said compromise national security and can put some people at risk.

Past WikiLeaks releases of classified U.S. documents on related to Iraq and Afghanistan have given a battlefield view of both conflicts and sensitive intelligence, but contained few startling revelations.

CREATING TENSION

State Department spokesman P.J. Crowley said Washington was assessing the implications of what WikiLeaks may reveal and was notifying foreign governments “that a release of documents is possible in the near future.”

“We decry what has happened. These revelations are harmful to the United States and our interests. They are going to create tension in our relationships,’ Crowley said. “We wish that this would not happen but we are obviously prepared for the possibility that it will.”

Both the State Department and the Pentagon confirmed they had been in touch with lawmakers on Capitol Hill to inform them of what may be coming.

Sources said three international news organizations which previously published stories based on classified U.S. government documents acquired by WikiLeaks -- the New York Times, Britain’s Guardian newspaper and the German weekly news magazine Der Spiegel -- were given access the documents some time ago by Julian Assange, the Australian-born computer hacker who says he is WikiLeaks’ founder and leader.

Two of the sources said Assange has also made the documents available to at least two other European publications -- the newspapers El Pais of Spain and Le Monde of France.

Assange did not immediately reply to an email seeking comment.

The New York Times, Guardian and Der Spiegel are trying to coordinate when they release their first stories about the material -- likely to be next week -- but one of the sources said that it is unclear whether Le Monde and El Pais will be publishing on the same schedule.

The sources said the documents -- which also report on other local controversies beyond allegations of corruption -- may result in more international uproar than did the earlier release by WikiLeaks of Pentagon reports on the conflicts in Iraq and Afghanistan.

Asked by e-mail to comment on the latest anticipated WikiLeaks release, New York Times Executive Editor Bill Keller told Reuters: “If we had a big story in the works, we’d be disinclined to discuss it before publication.”