LOS ANGELES (Reuters) - Slammed by all sides, from high-ranking Republicans to rival networks, CBS News vowed on Wednesday to answer questions about the authenticity of documents it aired in a story challenging President Bush's military service during the Vietnam War.

A week after "6O Minutes II" aired a Dan Rather report citing memos from Bush's former Texas Air National Guard squadron commander, CBS News president Andrew Heyward said the network was satisfied that the documents were accurate but said he recognized the public had doubts about them.

In a statement broadcast on CBS, Heyward said, "We established to our satisfaction, which is a high standard, that the memos are accurate or we wouldn't have put them on television, we wouldn't have done the report. There was a great deal of corroborating evidence from people in the position to know about the accuracy of the memos."

But he added, "Having said that, given all of the questions about them, I believe and we believe that we should redouble our efforts to answer those questions, so that's what we are doing."

In a statement to CBS affiliates, Rather said he believed the documents were legitimate but echoed Heyward's pledge to answer critics.

"There are serious ... people who have raised serious questions about the documents and I am determined to get all the information we can about the documents. But right now, about the information, there is no dispute," he said.

The four memos, purportedly written and signed by the late Air National Guard Lt. Col. Jerry Killian, said that he was under pressure from his superiors to "sugar coat" Bush's service record after Bush, then a Guard pilot, was grounded for his failure to perform to standards or to take a physical.

Immediately after the report was aired last Wednesday, conservatives and competing news organizations challenged the authenticity of the documents.

They said that comparisons of the Killian memos with other documents from Bush's National Guard service revealed inconsistencies in terminology and word processing techniques.

A FORGERY?

The Los Angeles Times in an editorial on Wednesday flatly declared that "CBS News was had" and in a news story quoted Killian's now 86-year-old secretary Marian Carr Knox as saying she thought the documents were forgeries even though the information in them was accurate. She did not say why she thought they were fake.

Interviewed, as well, on CBS News and by The New York Times, Knox said that Killian did indeed object to efforts to gloss over Bush's shortcomings and failures, even though he personally liked the then young airman.

Knox also said that Killian kept personal files on Bush in a desk drawer as "a way of covering his back" in anticipation of later questioning and that she did not know what was in those files.

Speaking of the memos used by CBS, Knox told The New York Times, "The information in them is correct. ... It's not anything I wrote because there are terms in there not used by Guards. .... It looks like someone may have read the originals and put them together."

In her later CBS interview, Knox added that Killian wrote a memo directing Bush to take a physical, which he failed to do.

Knox said, "It seems to me Bush felt he was above reproof." She added that Bush's attitude was "that he didn't really have to go by the rules. It seemed that way to me."

California Republican Congressman Chris Cox has called for a probe of the network's use of what he termed was "apparently forged documents concerning the service record of President Bush intended to unfairly damage his reputation and influence the outcome of the 2004 presidential election."

In an interview with the New York Observer weekly newspaper, Rather, one of the giants of American broadcasting, called on Bush to answer the questions the memos raised about his Vietnam-era service instead of having surrogates question the veracity of the memos.

"With respect: answer the questions," Rather said, adding, "We've heard what you have to say about the documents and what you've said and what your surrogates have said, but for the moment, answer the questions."