WikiLeaks is believed to be preparing to release around 400,000 classified Pentagon documents on the Iraq war this week, the Associated Foreign Press reported Friday.

The release, which could come as early as Sunday, will be the whistleblower website’s largest publication of classified materials to date, far exceeding its release in July of 77,000 U.S. military documents on the war in Afghanistan.

In preparation for the potential impact of the reports going public, Pentagon officials set up a 120-person taskforce several weeks ago, the AFP said. The team has been searching the Iraq war database to “determine what the possible impacts might be,” Col. David Lapan, a Pentagon spokesman, told the AFP.

In a letter released Friday, Pentagon officials stated that no U.S. intelligence sources or practices were compromised by WikiLeaks July document release, but that the military thinks the leaks could still cause significant damage to U.S. security interests.

The letter, obtained by The Associated Press, suggested that some of the Obama administration's worst fears about the July disclosure of almost 77,000 secret U.S. war reports had so far failed to materialize.

Defense Secretary Robert Gates reported these conclusions in an Aug. 16 letter to Sen. Carl Levin, chairman of the Senate Armed Services Committee, who had requested a Pentagon assessment.

Questions persist about whether the disclosure undermined U.S. officials' ability to maintain the allegiance of allies and people from other countries who take risks to cooperate with the U.S.

"The mere fact of the disclosure erodes confidence in the ability of the military to keep secrets," said Steven Aftergood, whose Secrecy News blog tracks trends in government openness.

"And that can have subtle but real effects on recruitment of sources and on maintenance of relationships with individuals and with other security services," he added. "So it's something they have to take seriously."

U.S. officials warned of dire consequences in the days following the July leak. In his letter to Levin, Gates struck a more measured tone in describing the impact.

"Our initial review indicates most of the information contained in these documents relates to tactical military operations," Gates wrote, suggesting the materials did not include the most sensitive kinds of information.

"The initial assessment in no way discounts the risk to national security; however, the review to date has not revealed any sensitive intelligence sources and methods compromised by this disclosure," he added.

A Pentagon spokesman, Marine Col. David Lapan, said Friday that the assessment of the July documents is still valid, even after a more thorough review. A special task force led by the Defense Intelligence Agency combed the posted reports for weeks to determine what might have been compromised.

Lapan said the since the Aug. 16 letter, Gates has kept members of Congress and their staffs apprised of the Pentagon's document review through phone calls, personal contacts and briefings.

Names of intelligence sources generally are classified at a higher level than the secret-level documents published by WikiLeaks. The documents provided a ground-level view of the war, from 2004 through 2009, based largely on narrow intelligence reports and other battlefield materials.

Gates noted that the documents contained the names of "cooperative Afghan nationals." These were not secret intelligence sources but Afghans who had decided to cut their ties to the Taliban.

The Taliban later vowed to punish these individuals, if the reports proved true.

"We assess this risk as likely to cause significant harm or damage to the national security interests of the United States and are examining mitigation options," Gates wrote. "We are working closely with our allies to determine what risks our mission partners may face as a result of the disclosure."

So far, the Pentagon has not reported any incidents of reprisals against Afghans named in the leaked documents.

Gates told a news conference on July 29, just a few days after the documents were posted by WikiLeaks, that he had enlisted the help of the FBI to investigate a leak with "potentially dramatic and grievously harmful consequences."

"The battlefield consequences of the release of these documents are potentially severe and dangerous for our troops, our allies and Afghan partners, and may well damage our relationships and reputation in that key part of the world," he said. "Intelligence sources and methods, as well as military tactics, techniques and procedures, will become known to our adversaries."

At the same news conference, Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, said the WikiLeaks operators could face blame for any deadly consequences.

"The truth is, they might already have on their hands the blood of some young soldier or that of an Afghan family," Mullen said.

More recently, U.S. intelligence officials have said the July disclosures sharpened a debate over how far to go in sharing sensitive information within the government, a practice that expanded after Sept. 11, 2001, in order to help prevent future terrorist attacks.

The Associated Foreign Press and the Associated Press contributed to this report.