WASHINGTON, July 28 - A 2004 dispute over the National Security Agency’s secret surveillance program that led top Justice Department officials to threaten resignation involved computer searches through massive electronic databases, according to current and former officials briefed on the program.

It is not known precisely why searching the databases, or data mining, raised such a furious legal debate. But such databases contain records of the phone calls and e-mail messages of millions of Americans, and their examination by the government would raise privacy issues.

The N.S.A.’s data mining has previously been reported. But the disclosure that concerns about it figured in the March 2004 debate helps to clarify the clash this week between Attorney General Alberto R. Gonzales and senators who accused him of misleading Congress and called for a perjury investigation.

The confrontation in 2004 led to a showdown in the hospital room of then Attorney General John Ashcroft, where Mr. Gonzales, the White House counsel at the time, and Andrew H. Card Jr., then the White House chief of staff, tried to get the ailing Mr. Ashcroft to reauthorize the N.S.A. program.

Mr. Gonzales insisted before the Senate this week that the 2004 dispute did not involve the Terrorist Surveillance Program “confirmed” by President Bush, who has acknowledged eavesdropping without warrants but has never acknowledged the data mining.

If the dispute chiefly involved data mining, rather than eavesdropping, Mr. Gonzales’ defenders may maintain that his narrowly crafted answers, while legalistic, were technically correct.

But members of the Senate Intelligence Committee, who have been briefed on the program, called the testimony deceptive.

“I’ve had the opportunity to review the classified matters at issue here, and I believe that his testimony was misleading at best,” said Senator Russ Feingold, Democrat of Wisconsin, joining three other Democrats in calling Thursday for a perjury investigation of Mr. Gonzales.

“This has gone on long enough,” Mr. Feingold said. “It is time for a special counsel to investigate whether criminal charges should be brought.”

The senators’ comments, along with those of other members of Congress briefed on the program, suggested that they considered the eavesdropping and data mining so closely tied that they were part of a single program. Both activities, which ordinarily require warrants, were started without court approval as the Bush administration intensified counterterrorism efforts soon after the Sept. 11 attacks.

A half-dozen officials and former officials interviewed for this article would speak only on the condition of anonymity, in part because unauthorized disclosures about the classified program are already the subject of a criminal investigation. Some of the officials said the 2004 dispute involved other issues in addition to the data mining, but would not provide details. They would not say whether the differences were over how the databases were searched or how the resulting information was used.

Nor would they explain what modifications to the surveillance program President Bush authorized to head off the threatened resignations by Justice Department officials.

An agency spokesman declined to comment on the data mining issue but referred a reporter to a statement issued earlier that Mr. Gonzales had testified truthfully.

The Justice Department announced in January that eavesdropping without warrants under the Terrorist Surveillance Program had been halted, and that a special intelligence court was again overseeing the wiretapping. The N.S.A., the nation’s largest intelligence agency, generally eavesdrops on communications in foreign countries. Since the 1978 passage of the Foreign Intelligence Surveillance Act, known as FISA, any eavesdropping to gather intelligence on American soil has required a warrant from the special court.

In addition, court approval is required for the N.S.A. to search the databases of telephone calls or e-mail records, usually compiled by American phone and Internet companies and including phone numbers or e-mail addresses, as well as dates, times and duration of calls and messages. Sometimes called metadata, such databases do not include the content of the calls and e-mail messages - the actual words spoken or written.

Government examination of the records, which allows intelligence analysts to trace relationships between callers and identify possible terrorist cells, is considered less intrusive than actual eavesdropping. But the N.S.A.’s eavesdropping targeted international calls and e-mail messages of people inside the United States, while the databases contain primarily domestic records. The conflict in 2004 appears to have turned on differing interpretations of the president’s power to bypass the FISA law and obtain access to the records.

President Bush has asserted that both his constitutional powers as commander in chief and the authorization for the use of military force passed by Congress after the Sept. 11 attacks gave him legal justification for skirting the warrant requirement. Critics have called the surveillance illegal because it does not comply with the FISA law.

The first known assertion by administration officials that there had been no serious disagreement within the government about the legality of the N.S.A. program came in talks with New York Times editors in 2004. In an effort to persuade the editors not to disclose the eavesdropping program, senior officials repeatedly cited the lack of dissent as evidence of the program’s lawfulness.

In December 2005, The Times published articles describing the program, the data mining and the internal legal debate. The newspaper reported that the N.S.A. had combed large volumes of telephone and Internet traffic in search of patterns that might point to terrorism suspects.

Civil liberties groups, Congressional Democrats and some Republicans reacted to the disclosures with outrage, accusing the administration of operating an illegal surveillance program inside the United States. The uproar grew when USA Today reported in May 2006 more details of the N.S.A.’s acquisition from telephone companies of the phone call databases. In response to the articles, Mr. Bush confirmed the eavesdropping, saying it was limited to communications in and out of the United States involving people suspected of ties to Al Qaeda. He did not, however, confirm the data mining, nor has any other official done so publicly.

Mr. Gonzales defended the surveillance in an appearance before the Senate Judiciary Committee in February 2006, saying there had been no internal dispute about its legality. He told the senators: “There has not been any serious disagreement about the program that the president has confirmed. There have been disagreements about other matters regarding operations, which I cannot get into.”

By limiting his remarks to “the program the president has confirmed,” Mr. Gonzales skirted any acknowledgment of the heated arguments over the data mining. He said the Justice Department had issued a legal analysis justifying the eavesdropping program.

Mr. Bush and other officials also have repeatedly cited Justice Department reviews as evidence of their care in overseeing the program, never mentioning the bitter conflict that unfolded behind the scenes.

Mr. Gonzales’s 2006 testimony went unchallenged publicly until May of this year, when James B. Comey, the former deputy attorney general, described the March 2004 confrontation to the Senate Judiciary Committee.

Mr. Comey had refused to sign a reauthorization for the N.S.A. program when he was standing in for Mr. Ashcroft, who was hospitalized for gall bladder surgery.

Mr. Comey described an intense fight that prompted the top leaders of the Justice Department to consider resigning in protest. Mr. Gonzales and Mr. Card visited the bedside of Mr. Ashcroft, who was in pain and under sedation, to seek his signature on the reauthorization.

Mr. Ashcroft refused to do so. Mr. Comey testified that he thought the White House officials were trying to take advantage of a sick man.

On Tuesday, to respond to Mr. Comey’s account, Mr. Gonzales testified in a Senate appearance that he went to the hospital only after meeting with Congressional leaders about the impending deadline for the reauthorization. He said the consensus was that the program should go on, so he felt he had no choice but to seek Mr. Ashcroft’s approval.

At the hearing, Mr. Gonzales faced harsh questioning about why he had not previously acknowledged the 2004 standoff. In response, he asserted once again that there had not been disagreements about the surveillance program, insisting that the dispute involved “other intelligence activities.”

After the hearing, Senator Patrick J. Leahy, Democrat of Vermont and chairman of the Judiciary Committee, sent Mr. Gonzales a transcript of his testimony with pointed instructions - to “correct, clarify or supplement your answers so that, consistent with your oath, they are the whole truth.”

© 2007 The New York Times