Anxious that Wikileaks may be on the verge of publishing a batch of secret State Department cables, investigators are desperately searching for founder Julian Assange. Philip Shenon reports. Plus, Daniel Ellsberg tells The Daily Beast: "Assange is in Some Danger."

Pentagon investigators are trying to determine the whereabouts of the Australian-born founder of the secretive website Wikileaks for fear that he may be about to publish a huge cache of classified State Department cables that, if made public, could do serious damage to national security, government officials tell The Daily Beast.

The officials acknowledge that even if they found the website founder, Julian Assange, it is not clear what they could do to block publication of the cables on Wikileaks, which is nominally based on a server in Sweden and bills itself as a champion of whistleblowers.

“We’d like to know where he is; we’d like his cooperation in this,” one U.S. official said of Assange.

American officials said Pentagon investigators are convinced that Assange is in possession of at least some classified State Department cables leaked by a 22-year-old Army intelligence specialist, Bradley Manning of Potomac, Maryland, who is now in custody in Kuwait.

And given the contents of the cables, the feds have good reason to be concerned.

As The Daily Beast reported June 8, Manning, while posted in Iraq, apparently had special access to cables prepared by diplomats and State Department officials throughout the Middle East, regarding the workings of Arab governments and their leaders, according to an American diplomat.

The cables, which date back over several years, went out over interagency computer networks available to the Army and contained information related to American diplomatic and intelligence efforts in the war zones in Afghanistan and Iraq, the diplomat said.

American officials would not discuss the methods being used to find Assange, nor would they say if they had information to suggest where he is now. "We'd like to know where he is; we'd like his cooperation in this," one U.S. official said of Assange.

Assange, who first gained notoriety as a computer hacker, is as secretive as his website and has no permanent home.

He was scheduled to speak Friday in Las Vegas at an Investigative Reporters and Editors conference. But the group’s executive director, Mark Horvit, tells The Daily Beast that Assange canceled the appearance—he was on a panel to discuss anonymous sources—within the last several days as a result of unspecificed “security concerns.” Horvit said he communicated with Assange through email and did not know where he might be.

Last week, Assange was scheduled to join famed Pentagon Papers leaker Daniel Ellsberg for a talk at New York's Personal Democracy Forum. Assange appeared via Skype from Australia instead, saying lawyers recommended he not return to the United States.