(Reuters) - WikiLeaks' next assault on Washington may highlight U.S. government reports on suspected militants held at Guantanamo Bay, which some U.S. officials worry could show certain detainees were freed despite intelligence assessments they were still dangerous.
The leaks could be an embarrassment to President Barack Obama's administration, already angered over WikiLeaks document dumps of U.S. State Department cables, as it seeks to fulfill a 2-year-old pledge to close the prison and either release the foreign terrorism suspects or move them elsewhere.
WikiLeaks founder Julian Assange, jailed in Britain this week, has told media contacts he has a large cache of U.S. government reports about inmates at the detention facility at Guantanamo Bay, Cuba, known as GITMO, the last of four major tranches of U.S. government documents which WikiLeaks had acquired and at some point would make public.
"He's got the personal files of every prisoner in GITMO," said one person who was in contact with Assange earlier this year.
Officials at the Pentagon and U.S. intelligence agencies had no immediate comment.
People familiar with Assange's dealings with the media said they had no indication he had already given journalists access to the Guantanamo material. In the past, large document dumps by WikiLeaks were made available initially to a small group of media.
Several U.S. government sources said there was concern Assange's material could include highly sensitive "threat assessments" by U.S. intelligence agencies gauging the likelihood that specific inmates would return to militant activities if set free.
These assessments, if published, could prove damaging in a number of ways, including revelations that could theoretically put in jeopardy U.S. intelligence sources and methods.
They could further embarrass the U.S. government if they show that detainees deemed likely to return to terrorism were released and subsequently involved in anti-U.S. violence.
It is unclear what time period may be covered by the Guantanamo documents believed to be in WikiLeaks' possession.
The prison at a U.S. naval base in Cuba was opened to house prisoners taken in the U.S.-led Afghan war launched by President George W. Bush soon after the September 11, 2001, attacks on the United States. It has been controversial as a legal limbo, and Obama said on taking office in January 2009 that he wanted to close it in a year.
BACK TO THE BATTLEFIELD
This week the office of the Director of National Intelligence, the government's top intelligence official, released statistics showing that one in four of the 598 detainees released from Guantanamo are either suspected or confirmed to have become re-engaged in "terrorist or insurgent activities" after their release.
U.S. agencies believe that 83 remain at large.
WikiLeaks has already released three batches of classified U.S. documents, including Pentagon reports on the wars in Afghanistan and Iraq and 250,000 State Department cables, whose recent release is currently roiling the diplomatic world.
WikiLeaks began posting material on numerous mirror websites around the world after one of their main U.S.- based hosts, Amazon, cut them off for violating terms of service.
Assange, in British custody after sexual misconduct allegations involving two Swedish women, has threatened to release a deeply encrypted "insurance file," believed to be yet another massive collection of government data, if WikiLeaks' existence is threatened. It is not known whether this file contains Guantanamo material.
On Wednesday, Assange's lawyer, Mark Stephens, told Reuters that because WikiLeaks websites were still operating, there was no plan to release "insurance file" at the moment.
(Editing by Andrew Quinn and Doina Chiacu)