Within the next few days, CBS News expects to name an independent panel of experts to scrutinize its reporting of President Bush's National Guard service after its defenses for airing the explosive story crumbled.

Eleven days after questions surfaced about Dan Rather's (search) "60 Minutes" report, the network apologized Monday and said it could not vouch for the authenticity of documents impugning the president's Guard service.

Click here to read the CBS documents (pdf).

"I want to say, personally and directly, I'm sorry," a subdued Rather said Monday on the "CBS Evening News."

It was humbling for a news division that once ruled television, for TV's pre-eminent newsmagazine and for Rather himself, at 72 already struggling against fading ratings and influence.

Now CBS opens its doors to an outside panel that will assign blame.

"I think it will be helpful, given the attention this story has received, for cool, collected, independent voices of unchallenged integrity to examine the process," CBS News President Andrew Heyward (search) said.

The White House said the affair raises questions about the connection between CBS's source, retired Texas National Guard member Bill Burkett (search), and the Kerry campaign.

Kerry adviser Joe Lockhart (search) said he had spoken to Burkett at the request of Mary Mapes, producer for the story. But Lockhart said he did not recall speaking about the National Guard to Burkett, and ended the call after taking a few minutes of campaign advice.

Burkett, who did not respond to requests for comment from The Associated Press, told USA Today that he had agreed to turn over the documents to CBS if the network would help arrange a conversation with the Kerry campaign. CBS admitted giving Burkett's number to the campaign, but said it was not part of any deal.

Burkett admitted this weekend to CBS that he lied about obtaining the documents from another former National Guard member, the network said. CBS hasn't been able to conclusively tell how he got them or even definitely tell whether they're fakes. But the network has given up trying to defend them.

"Based on what we now know, CBS News cannot prove that the documents are authentic, which is the only acceptable journalistic standard to justify using them in the report," Heyward said. "We should not have used them."

CBS said it approached Burkett initially about the memos purportedly written by Bush's late squadron leader, Lt. Col. Jerry B. Killian (search). Several experts have dismissed the documents as fakes. Rather said Burkett was well known in National Guard circles for several years for trying to discredit Bush's military record.

Burkett, in an interview with Rather aired on the "CBS Evening News," said he was pressured by CBS to reveal his source for the documents, and "I simply threw out a name that was basically, I guess, to get a little pressure off for the moment."

He said he did not fake or forge any documents.

"I didn't totally mislead you," he said. "I did mislead you about one individual."

Burkett said he also insisted CBS authenticate the documents on its own. Two document experts consulted by CBS later said they raised red flags that network officials apparently disregarded. Rather acknowledged CBS failed to properly determine whether the documents were genuine.

Questions about the documents surfaced on the Internet soon after the piece aired. CBS stood by its story until last Wednesday, when it said there were some doubts about them and it merited further investigation.

Alex Jones, director of Harvard University's Shorenstein Center on the Press, Politics and Public Policy, said it appeared to be an honest mistake by CBS. But he said the network was too slow to respond.

"I think that their delaying and obvious resistance to acknowledge the evident realities has kept the story alive a lot longer than it needed to be and was a lot more damaging to CBS than it needed to be," he said.

White House press secretary Scott McClellan (search) said the White House appreciated CBS's expression of regret, but there were still serious questions about Burkett.

"Bill Burkett, who CBS now says is their source, in fact is not an unimpeachable source as was previously claimed," McClellan said. "Bill Burkett is a source who has been discredited and so this raises a lot of questions. There were media reports about Mr. Burkett having senior level contacts with the Kerry campaign."

The Kerry campaign has said it had nothing to do with the story.

Burkett, a Democrat, sent an e-mail last month to several Texas Democrats, saying he had passed along information to Max Cleland, a former Georgia senator and Kerry supporter, about information that would counter criticism of Kerry's Vietnam War service.

Cleland said Monday he does "not have any knowledge" about documents used to support the "60 Minutes" story.

Heyward told the AP he has "no reason to believe either the Kerry campaign or the Bush campaign was involved in this."

"A lot of reporting went into this story," Heyward said. "It's not as if one person's account was taken at face value."