Julian Assange opposed immediate publication of U.S. State Department cables out of fear that it would help confirm that Army private Bradley Manning had illegally passed the classified material to WikiLeaks, according to a new book written by journalists at the Guardian.

Assange expressed his concern during a June 22, 2010 meeting in Brussels with Guardian investigative reporter Nick Davies and also insisted that if they published the cables, the New York Times should publish them before foreign publications published them because he believed it would make it more difficult for the U.S. Justice Department to charge Manning under the Espionage Act.

The information is revealed in WikiLeaks: Inside Julian Assange’s War on Secrecy, written by the Guardian investigations editor David Leigh and reporter Luke Harding. The book provides the most comprehensive look yet at the back story behind WikiLeaks’s collaboration with media partners in publishing the largest leaks in the history of the United States, and also reveals for the first time the identity of the WikiLeaks insider who broke the organization’s security protocols by giving a copy of the cables to a freelance journalist who wasn’t supposed to have them.

Davies met with Assange after reading Wired.com’s excerpts of chat logs between Bradley Manning and ex-hacker Adrian Lamo in which Manning allegedly confessed to passing 260,000 U.S. State Department cables to WikiLeaks, as well as a tranche of hundreds of thousands of documents from the Iraq and Afghan wars. Davies wanted to broker a collaboration between his newspaper and WikiLeaks to publish the documents.

Although Assange had publicly denied possessing the U.S. cables, he admitted to Davies that he had them. But he was “concerned that publishing the leaked material might give the Pentagon investigators further evidence to work on” against Manning. Manning had been arrested in late May, but at the time Davies and Assange met, Manning had still not been charged with any crime.

“Assange said that if the Big Leak were to go ahead, he would want to control the Guardian’s timing: he didn’t want to publish too soon if this would damage Manning, but he was also prepared to post everything immediately if there was any kind of attack on WikiLeaks,” the authors write.

WikiLeaks had already published one cable in February 2010 that Manning told Lamo he had passed to the site. It was a classified cable titled “Reykjavik 9? that describes a U.S. embassy meeting with the government of Iceland. Manning had described the cable as a “test.”

In his June discussion with Davies, Assange claimed that WikiLeaks had been ready to post all of the remaining cables “for the past two weeks, but he was hesitating because, although he would never reveal whether Manning was a source, he was worried about the legal implications for the young soldier.”

If they did go forward with publication, Assange insisted that the New York Times should publish the cables five minutes before the Guardian and other foreign publications published them, because he felt it would make it more difficult for the U.S. Justice Department to indict Manning on Espionage Act charges.

About two weeks later, on July 6, Manning was charged with eight violations of federal criminal law, including allegedly abusing access to the Secret-level SIPR network to download at least 150,000 U.S. State Department cables and passing more than 50 classified diplomatic cables to an unauthorized party. He was also charged under the Espionage Act for downloading a classified video of a military operation in Iraq and transmitting it to a third party.

WikiLeaks and its media partners subsequently published the tranche of documents from Iraq and Afghan, and set a tentative date for publishing the cables sometime in October, since Assange believed the Army’s charges against Manning would be crystallized by then. He ultimately convinced the editors to delay publication until November so that he could prepare for the expected onslaught. “We have woken a giant by wounding one of its legs [the U.S. defense department] and the release of this material will cause the other leg [the state department] to stand up,” he told the Guardian.

In explaining his decision to publish the cables, despite the potential harm to Manning, Assange later told ABC in Australia that it would set a dangerous precedent to withhold publication just because a source or potential source had been arrested. “We cannot be in a position where upcoming publications can be affected by taking hostages,” he said. “Well I mean if a particular government wants to engage in abusive action, it engages in abusive action. But we have a promise to our sources that we will publish.”

The publication of the cables was ultimately complicated by the fact that a WikiLeaks insider violated the security chain established for the documents by passing them to an outside freelance reporter. The Guardian book reveals that Smari McCarthy — a member of the Icelandic Digital Freedoms Society who had been a programmer for WikiLeaks — was the inside leaker.

The leaked database caused a showdown between Assange and the Guardian after Assange learned that the insider had given the cables to Heather Brooke, an American journalist based in the UK. She passed them to the Guardian, essentially releasing the newspaper, in principle, from any prior agreements it had made to Assange about the documents.

According to a recent book published by WikiLeaks defector Daniel Domscheit-Berg, when WikiLeaks learned that an insider had passed the cables to Brooke, the organization made the insider sign a declaration saying the documents had been taken from him illegally. Domscheit-Berg didn’t name the insider in his book.

Asked about the accuracy of the Domscheit-Berg and Guardian accounts, Brooke, without confirming that McCarthy was her source, wrote in an e-mail to Threat Level that “The data was shown to me on a confidential basis to protect both my source and myself. Somehow Julian found out about this. He exposed my source to a newspaper (see the Guardian’s book) and I understand that the source was threatened by people working for Julian to sign some kind of document they’d drafted. I’ve also been threatened by Julian and ‘the Nanny’ who made dark intimations that because I hold an American passport I might find myself in a ‘difficult and potential risky position.’”

The “nanny” is a forty-something female friend from Assange’s past who has been described as someone who writes speeches for Assange and occasionally flies in to take care of situations he doesn’t want to deal with.

Brooke added that the comments from Assange and the nanny “led me to believe they were trying to scare me with a U.S. investigation, which, coming from them, was so rich with irony as to be laughable. Nevertheless it did prompt me to consult my lawyer. I was reassured that these were empty threats and I had nothing to worry about.”

Brooke ended up signing an exclusivity agreement with the Guardian so that she would not scoop the newspaper on its coverage or take the cables elsewhere. She’s currently writing her own book about WikiLeaks.

Among other revelations in the Guardian book:

• Wikileaks gave Daniel Ellsberg an encrypted copy of the cable database that he was going to dramatically present to the New York Times — presumably in the presence of news cameras — as a kind of homage to the former military analyst’s famed leaking of the Pentagon Papers to that newspaper in 1971. Assange told the Guardian that Ellsberg was going to present the cable database to the Times “in a piece of political theater.”

• Assange, or someone associated with WikiLeaks, apparently sniffed or hacked into the e-mail account of a Guardian reporter and used information in the e-mail to convince the Guardian editors that they needed to improve their security. The incident occurred after Assange met with one of the Guardian reporters at a hotel in Brussels. The reporter sent an e-mail back to his editors that Assange was willing to discuss collaboration. The next day the reporter met with Assange.

Assange was in mischievous good spirits. The former hacker told Traynor: “You guys at the Guardian, you have got to do something about your security. You have got to get your email secure and encrypted.”

“He knew the contents of the email I had sent to London,” Traynor said, somewhat amazed. “He was showing off, but also expressing concern.”

The revelation seems to mirror a recent account from The New York Times that the e-mail accounts of at least three newspaper people associated with the WikiLeaks publication project appeared to have been hacked. Keller suggested Assange and WikiLeaks could have been behind the intrusions.

• Assange insisted that the cables be released gradually, not in a “big dump,” and that the order of the releases be manipulated so that it didn’t appear that the leak was anti-American. “He didn’t want WikiLeaks to seem obsessed with America,” the authors write. Assange had already come under criticism from WikiLeaks insiders for focusing all of the organization’s 2010 leaks on the United States.

There are security exposés and abuses by other countries, these bad Arab countries, or Russia,” he said. “That will set the initial flavor of this material. We shouldn’t go exposing, for example, Israel during the initial phase, the initial couple of weeks. Let the overall framework be set first. The exposure of these other bad countries will set the tone of American public opinion. In the initial couple of weeks the frame is set that will color the rest of it.”

• A controversial Holocaust-denier named Israel Shamir invoiced WikiLeaks for 2,000 euros for “services rendered — journalism.” Shamir had been given copies of cables related to Russia and post-Soviet nations. He told the Guardian that his job for WikiLeaks was “to read and analyze the cables from Moscow.” But Shamir reportedly later tried to peddle the cables to Russian reporters for $10,000, claiming he was WikiLeaks’ Russian representative. He also authored articles that pilloried two Swedish women who had accused Assange of rape and sexual coercion, suggesting the women were part of a CIA honey trap. The articles were used by Assange supporters to attack the integrity of the women.

• Weeks before the cables were published, the U.S. State Department appeared to be ignorant of which cables WikiLeaks actually possessed. At one point the private secretary to Secretary of State Hillary Clinton asked the Guardian editors pointedly, “Are you going to give us the numbers of the cables [you have] or not?” The editors replied, “No, we’re not.”

Officials feared the cables covered the period through the end of May 2010, when Manning was arrested, and were apparently particularly concerned that a cable about the U.K.’s new prime minister David Cameron was among the documents. In anticipation of the release, officials sheepishly briefed UK officials to prepare them for what might be exposed in the cable. But the documents turned out to only cover up to February 2010, leaving the Cameron document safely ensconced in a U.S. government network.

“We were amazed about how little the United States knew about what we were doing,” one member of the Guardian team later said. “They clearly had no idea which data set we had. They massively overbriefed about what was in the cables.”