Washington ? Bob Woodward’s version of when and where he learned the identity of a CIA operative contradicts a special prosecutor’s contention that Vice President Dick Cheney’s top aide was the first to make the disclosure to reporters.

Attorneys for the aide, I. Lewis “Scooter” Libby, described Wednesday’s statement by the Washington Post’s assistant managing editor as helpful for their defense, although Libby is charged with lying to a grand jury and the FBI, not with disclosing the CIA official’s name.

Woodward, a Pulitzer Prize winning reporter, said he had not told his bosses until last month that he had learned about Valerie Plame’s identity and her work at the CIA more than two years ago from a high-level Bush administration official.

When he learned Plame’s name, Woodward said Wednesday, he was in the middle of finishing a book and didn’t want to be subpoenaed to testify.

Woodward made his name with his coverage of the Watergate scandal during the Nixon administration. He kept secret for decades the identity of “Deep Throat,” a key source in that reporting.

To critics who are taking shots at him, Woodward said, “Journalism is a contact sport. I was 29 when people who really knew how to shoot were around,” referring to Watergate.

Because his source in the leak case has refused to be identified publicly, Woodward said his hands are tied.

Columnist Robert Novak disclosed Plame’s identity and her work at the CIA on July 14, 2003, eight days after her husband, Joseph Wilson, a former ambassador, had accused the White House of misrepresenting intelligence to justify the Iraq war.

Libby, Cheney’s former chief of staff, was indicted last month on charges that he lied to FBI agents and a grand jury about when he learned Plame’s identity and how he subsequently disclosed it to reporters.

Legal experts said Wednesday the disclosure that Woodward had a source – who was not Libby – could be used by Libby’s attorneys to bolster their claim that Plame’s identity was common knowledge among government officials and reporters.