CBS News anchor Dan Rather apologized yesterday for a "mistake in judgment" in relying on apparently bogus documents for a "60 Minutes" report charging that President Bush received favorable treatment in the National Guard, ending a nearly two-week-long defense of the network's journalistic conduct that media analysts say has badly hurt its credibility.

CBS also acknowledged for the first time that its source was retired Texas National Guard official Bill Burkett, who Rather said in an interview had "misled" and "lied to" the network in describing how he obtained the purported 30-year-old memos said to have been signed by Bush's late squadron commander.

"I deeply regret I wasn't as good on this story as I should have been," Rather said. Asked whether he felt tarnished, he replied: "I have confidence that those people who don't have a specific partisan political or ideological agenda will understand what happened, how it happened, and I think they have confidence in CBS's credibility and my own. I do have a lifetime of reporting."

Burkett told CBS in an interview aired last night that he "threw out a name" of a bogus source because Rather's producer, Mary Mapes, had "pressured me to a point to reveal that source." Burkett said he had "insisted" that the memos "be authenticated" by CBS.

Mapes also put Burkett in touch with a senior official in John F. Kerry's presidential campaign after telling him that Burkett had been "helpful" on what was then CBS's upcoming story about Bush and the National Guard. The Kerry campaign confirmed her unusual go-between role but said Burkett provided no information about Bush.

What remains unclear is who provided the documents to Burkett and whether the memos were forged in a calculated effort to discredit Bush in the final weeks of his reelection effort. Rather said Burkett previously told CBS that the source was a former Guardsman who was out of the country and could not be reached by the network, and that the new source Burkett named is "one we cannot verify." CBS is still not saying that the memos are forgeries, only that the network cannot confirm they are authentic.

CBS News President Andrew Heyward acknowledged that "60 Minutes" had rushed the story to air on Sept. 8 -- five days after Mapes obtained the memos -- despite warnings from some of its document analysts that the memos may not have been produced on a 1970s government typewriter. "In retrospect, we shouldn't have used the documents, and we clearly should have spent more time and more effort to authenticate them," Heyward said.

CBS staff members, many of whom felt the apology was overdue, were relieved to discover that Burkett had admitted lying to the network, if only to spread the blame.

As Rather conceded, "The question is, why didn't you do it sooner? The story is true. I believed in the story. . . . What kind of reporter would I be -- what kind of person would I be -- if I put something on the air that I believed and then didn't stand behind it? At the first sign of pressure, you run, you cave, you fold? I don't do that."

At the same time, he said, "The fact that copies of the documents could be true was not enough. We needed to be able to prove they were authentic."

"Obviously," Rather added, "I would like to get the original documents if they still exist."

Heyward declined to say whether Rather or anyone else would be disciplined, or whether his news division would change its procedures, saying he wants to see the recommendations of outside investigators he plans to appoint.

Burkett once sued the Guard over medical benefits and previously contended that he had overheard Guard officials talking about sanitizing Bush's medical records -- a contention Texas Guard officials strongly dispute.

Under pressure from CBS, Burkett has now told the network, Rather said, that "I eventually gave you a name to protect the 'real' person."

Burkett has urged Democratic activists to wage "war" against Republican "dirty tricks," and contacted former Democratic senator Max Cleland (Ga.) in August to offer information to the Kerry campaign.

White House communications director Dan Bartlett said CBS's admission "begs the question as to where the documents came from." He noted that Kerry campaign manager Mary Beth Cahill made a congratulatory call to former Texas lieutenant governor Ben Barnes, a Kerry fundraiser, after Barnes appeared in the same "60 Minutes" segment. Barnes had nothing to do with the documents.

"There seemed to be a lot of high-level interest in the Kerry campaign and among Democrats, and the question is, was there more than just interest? Were there any high-level contacts?" Bartlett asked. White House spokesman Scott McClellan said Burkett was a "discredited" source well before he spoke to "60 Minutes."

Kerry senior adviser Joe Lockhart said that after receiving a call from Mapes on Sept. 4, he called Burkett, who urged the campaign to be more aggressive in responding to attacks on Kerry's Vietnam War record. Lockhart said he is "99.9 percent sure" that Burkett did not mention Bush and the Guard, and accused the Bush campaign of making "baseless charges" of Democratic involvement. Burkett told USA Today that his contact with Lockhart was part of an "understanding" with CBS in exchange for providing the documents.

Critics seized on CBS's acknowledgment of failure. Conservative activist Bill Bennett, whose Salem Radio Network show reaches 100 stations, said that "bias isn't the point. This is corruption. Corruption is when you don't adhere to basic and fundamental standards. They so much wanted it to be true. . . . They were doing what they accused Richard Nixon of doing: stonewalling."

Even liberal columnists are not defending Rather and CBS. "They've handled this about as badly as could be imagined," Boston Phoenix media writer Dan Kennedy said. "They were way too late in acknowledging there may be problems with this. The short-term damage is just horrendous. You have a large percentage of the public believing -- falsely, I would argue -- that the media are suffused with liberal bias, and this just plays right into that."

Media critic Michael Wolff, who writes for Vanity Fair, said CBS executives "are unacquainted with the reality of the modern news business -- that if you're exposed on any point, you're going to get ripped apart." But he said he believes the underlying allegations reported by CBS -- that Bush had received favorable treatment in the Guard -- are accurate.

Alex S. Jones, director of Harvard's Shorenstein media center, disagreed, saying it would be a "mistake" for CBS to keep defending the underlying story. "To the extend that Dan Rather steps up and takes the bullet, his credibility will be salvaged," Jones said. "If he is perceived as ultimately not willing to take responsibility, that will be more damaging for him."

Jones added that "somebody's head is going to have to roll," but that it was unlikely to be Rather's because "I don't expect the anchor to be the guy who understands every aspect of the story."

In a further sign of the turmoil at CBS, some staff members at the original Sunday "60 Minutes" say their program has been unfairly blemished by the Wednesday spin-off, which began in 1999 as "60 Minutes II."

"I think it is safe to say that the overwhelming feeling among correspondents and producers on the Sunday program is that we would not have made the same mistakes," correspondent Steve Kroft said. He added: "It's hard to know at this point exactly what went wrong, because the Wednesday show is an entirely separate broadcast with entirely different people, and brand-new management. But something clearly went wrong with the process."

Josh Howard, who runs "60 Minutes" Wednesday, said producer Mapes had not told him that Burkett was the source and that this was "probably one of many things I would do differently next time." As for Burkett's charge that Mapes, who has declined all interview requests, pushed him too hard, Howard said: "If anything, we didn't push hard enough."

Rather, who got into an on-air shouting match with Vice President George H.W. Bush during the 1988 presidential campaign, dismissed criticism that he bears a grudge against the family. "I believe overwhelmingly, people, even people who don't like me, know I'm fiercely independent and I'm not motivated by politics," he said. "I'm motivated by news."

Heyward, noting that other news organizations had restored their reputation after journalistic embarrassments, said he does not think the mistake will be a "permanent blot" on CBS's reputation.

"I deeply regret I wasn't as good on this story as I should have been," CBS anchor Dan Rather said about the National Guard controversy.