WASHINGTON (CNN) -- Washington Post reporter Bob Woodward said Monday he kept his conversation with a Bush administration official about the identity of a CIA operative secret for two years because "I was trying to avoid being subpoenaed."
Woodward said on CNN's "Larry King Live" he also didn't tell his boss, executive editor Leonard Downie Jr., about the source, a decision he called a mistake.
"And I should have -- as I have many, many times -- taken him into my confidence," he said. "And I did not."
Woodward said he first realized he had to go to his editor after the October indictment of I. Lewis "Scooter" Libby, Vice President Dick Cheney's chief of staff, on five felony charges. Libby subsequently resigned.
The indictment alleged Libby first leaked Plame's name to New York Times reporter Judith Miller on June 23, 2003. Miller recently resigned as well.
"I went, 'Whoa,' because I knew I'd learned about this in mid-June, a week, 10 days before," Woodward said.
Woodward said he went to his source and said, " 'Do you realize when we talked about this and exactly what was said?' And the source in this case ... said, 'I have to go to the prosecutor. I have to go to the prosecutor. I have to tell the truth.'
"And so I realized I was going to be dragged into this, that I was the catalyst. And then I asked the source, 'If you go to the prosecutor, am I released to testify?' And the source told me, 'Yes.' "
The source, however, did not say Woodward could release his name -- something Woodward said he wishes he could do.
"I would love it, but here is the issue," he said. "To get what's in the bottom of the barrel, you have to establish relationships of confidentiality with people at all levels of government. You have to establish relationships of trust."
At one point, King pressed Woodward to reveal the source. "Good try. Good try," Woodward said.
He added, "I pressed that source as much as you can."
Woodward, who along with Post colleague Carl Bernstein gained acclaim as an investigative reporter during the Watergate scandal in the 1970s, gave a deposition to a special prosecutor investigating the matter on November 14.
Woodward said the source made the 2003 comments in a "casual and offhand" nature, not as part of a conspiracy to smear the agent, Valerie Plame, and her husband, retired career diplomat Joseph Wilson, a Bush administration critic.
Woodward said he did not believe there was an "underlying crime" when his source first mentioned Plame's identity to him.
"When it all comes out -- and hopefully it will come out -- people will see how casual and off-hand this was," he said.
"Remember the investigation and the allegations that people have printed about this story is that there's some vast conspiracy to slime Joe Wilson and his wife, really attack him in an ugly way that is outside of the boundaries of political hardball.
"The evidence I had firsthand, a small piece of the puzzle I acknowledge, is that that was not the case."
Wilson has alleged otherwise, saying the administration intentionally leaked his wife's name to get back at him for raising questions about a key element of the administration's case for war -- that Saddam Hussein had sought to purchase uranium from the African country of Niger.
Woodward's belated admission to what he knew has prompted some to criticize his reporting, including the readers' advocate at the Post, who said he committed a "deeply serious sin" for not revealing his conversation with the source earlier.
"He has to operate under the rules that govern the rest of the staff -- even if he's rich and famous," ombudsman Deborah Howell wrote in Sunday's editions.
Downie has said Woodward, an assistant managing editor at the paper and the author of several nonfiction books, made a mistake by not revealing the information earlier and that he should not have appeared on television to discuss the case ahead of Libby's indictment.
In one of those appearances, on "Larry King Live," Woodward was asked October 27 by another reporter about a "bombshell" he was supposedly working on for the Post.
"I wish I did have a bombshell. I don't even have a firecracker. I'm sorry," Woodward said.
When asked Monday if his reputation had been damaged, Woodward said, "That's for other people to judge. I think the biggest mistake you can make in this sort of situation as a reporter is to worry about yourself."
