WASHINGTON — After almost two weeks of defending the authenticity of the documents, CBS News and Dan Rather on Monday apologized for airing paperwork they now say cannot be positively identified as records from President Bush's National Guard service.

Rather and CBS News President Andrew Heyward said the documents should not have been used on the air because retired Texas Air National Guard Lt. Col. Bill Burkett, who provided them, had lied about where he got them.

"Now, after extensive additional interviews, I no longer have the confidence in these documents that would allow us to continue vouching for them journalistically," Rather said in a statement noting CBS had been "misled on the key question of how our source for the documents came into possession of these papers."

Heyward said CBS News "cannot prove the documents are authentic" and the network will commission an independent review of the process by which the report was prepared.

Rather also issued an on-air apology Monday night.

The disputed documents purport to indicate that Bush had ignored an order to undergo a physical and failed to meet his Guard obligation in the early 1970s.

David Van Os, Burkett's lawyer, acknowledged on Monday that his client had misled CBS about where he got the documents in an effort to protect the source. But Van Os also said Burkett turned them over to CBS, without vouching for their authenticity, on the promise that the network would keep his name out of it and would independently verify their authenticity.

In an interview aired on CBS Evening News, Burkett told Rather "when I sat down with your staff for the first face-to-face session before I gave up any documents I wanted to know what you were going to do with them."

"And I insisted that they be authenticated," he added.

Said Rather, "The failure of CBS News to do just that, to properly scrutinize the documents and their source, led to our airing the documents when we should not have done so. It was a mistake CBS News deeply regrets."

In addition to not knowing if the documents were authentic, Burkett also could not positively identify the person who gave them to him earlier this year, according to Van Os.

"CBS did the slickest job of coaxing and pressuring him into showing the documents, and when Bill finally showed CBS the documents it was under two major conditions," Van Os said. They were a promise of anonymity for Burkett and assurances that they would check the documents' authenticity.