Bill O'Reilly and Washington Post associate editor Bob Woodward faced off in a testy debate Wednesday over the Post's reporting of classified information in stories about the Trump administration on Fox News' "The O'Reilly Factor."

At one point, O'Reilly asked Woodward if he believed the Post was being "used" when details of then-national security adviser Michael Flynn's phone calls to the Russian ambassador to the U.S. were leaked to the paper.

"Oh, wait a minute," Woodward answered. "Come on. That's BS."

"Well, who put it out, Bob?" O'Reilly asked. "Who put it out?"

"I don't know," Woodward eventually responded, later adding "this isn’t about being used. This is about what’s true."

Woodward, best known for helping to break the Watergate story that led to the resignation of Richard Nixon, insisted that recent stories the paper had published about Flynn as well as Attorney General Jeff Sessions had "been verified and ... presented in a careful way that does not harm national security."

"It’s impossible to report on foreign affairs or intelligence or what the Pentagon is doing and not deal with classified information," Woodward told O'Reilly.

"I don't believe that," the host responded.

"I’ve had presidents in Republican and Democratic administrations provide information that is technically classified," Woodward said. "And the question is, here, can it be done in a careful and fair way and I believe it has."

"Here’s the question from me," O'Reilly asked to close the discussion. "Does it damage the country? That's the question from me."