The Obama administration on Thursday informed CIA officials who used waterboarding and other harsh interrogation tactics on terror suspects that they will not be prosecuted, senior administration officials told The Associated Press.

Even before President Barack Obama took office in January, aides signaled his administration was not likely to bring criminal charges against CIA employees for their roles in the secret, coercive terrorist interrogation program. It had been deemed legal at the time through opinions issued by the Justice Department under the Bush administration.

But the statement being issued Thursday by Attorney General Eric Holder, the nation's chief law enforcement officer, is the first definitive assurance that those CIA officials are in the clear, as long as their actions were in line with the legal advice at the time.

The officials spoke about the Holder statement ahead of its release on condition of anonymity, so as not to pre-empt the attorney general.

The CIA has acknowledged using waterboarding, a form of simulated drowning, on three high-level terror detainees in 2002 and 2003, with the permission of the White House and the Justice Department. Former CIA Director Michael Hayden said waterboarding has not been used since, but some human rights groups have urged Obama to hold CIA employees accountable for what they, and many Obama officials and others around the world, say was torture.

The Holder statement was being issued by the Justice Department along with the release of four significant Bush-era legal opinions governing _ in graphic and extensive detail _ the interrogation of terror detainees, the officials said. One of the memos was produced by the Justice Department's Office of Legal Counsel in August 2002, the other three in 2005.

The memos, released to meet a court-approved deadline in a lawsuit against the government in New York by the American Civil Liberties Union, detail the dozen harsh techniques approved for use by CIA interrogators, the officials said. A statement from Obama was also being released along with Holder's comments and the documents.

One memo specifically authorized a method for combining multiple techniques, a practice human rights advocates argue is particularly harmful and crosses the line into torture even if any of the individual methods do not.

The Obama administration last month released nine legal memos related to the interrogation program, and probably will release more as the lawsuit proceeds. But the four released Thursday represent the fullest accounting by the government of the methods authorized and used, and is the complete list, the officials said.

There is very little redaction, or blacking out, of detail in the memos, the officials said.

The methods include keeping detainees naked for long periods, keeping them in a painful standing position for long periods, and depriving them of solid food. Other tactics included using a plastic neck collar to slam detainees into walls, keeping the detainee's cell cold for long periods, and beating and kicking the detainee. Sleep-deprivation, prolonged shackling, and threats to a detainee's family were also used.

Among the things not allowed in the memo were allowing a prisoner's body temperature or caloric intake to fall below a certain level, because either could cause permanent damage, the officials said.

The techniques were applied to 14 suspects considered very senior terrorists.

Many of the methods were detailed in a secret 2007 report by the International Committee of the Red Cross. The New York Review of Books recently obtained a copy of the report.

The ACLU suit has sought to use the Freedom of Information Act to shed light on the treatment of prisoners in U.S. custody abroad _ even though the Bush administration eventually abandoned many of the legal conclusions and the Obama administration has gone further to actively dismantle most of President George W. Bush's anti-terror program.

Obama has ordered the CIA's secret overseas prisons known as "black sites" closed, ended so-called "extraordinary renditions" of terrorism suspects if there is any reason to believe the third country would torture them, and restricted CIA questioners to only those interrogation methods and protocols approved for use by the U.S. military until a complete review of the program is conducted.

Also Thursday, Holder was formally revoking every legal opinion or memo issued during Bush's presidency that justified interrogation programs. Obama had already said his administration would not rely upon them.

Still, the documents have been the subject of a long, fierce debate in and outside government over how much officials should say about the tough treatment of detainees.

The Bush administration held the view that the president had the authority to claim broad powers that could not be checked by Congress or the courts in order to keep Americans safe. Obama and Holder, among others, have said that the use of such unchecked powers has actually made Americans less safe, by increasing anti-U.S. sentiment, endangering American troops when captured and handing terrorists a recruiting tool.

Still, the officials described the president's process of deciding how much to release in response to the suit as a very difficult one. Four weeks in the making, the process resulted in intense debates involving the president, Cabinet members, lower-level officials and even former administration officials.

Obama was concerned that releasing the information could endanger ongoing operations, American personnel or U.S. relationships with foreign intelligence services. CIA officials, in particular, needed reassuring, the officials said.

But in the end, the view of the Justice Department prevailed, that the FOIA law required the release and that the government would be forced to do so by the court if it didn't do so itself, the officials said. Also, Obama was reassured about the potential national security implications by the fact that much of the information contained in the memos has already been widely reported and by the fact that the program itself no longer exists.