Watergate reporter Carl Bernstein cautioned that it will take some time to fully know the truth about the explosive BuzzFeed report about President Donald Trump and his former attorney Michael Cohen’s congressional testimony.

“It’s going to take time before we fully understand what the exact truth is here in terms of the facts relating to Mr. Cohen and whether or not the president directed him to lie” to Congress about Trump Tower Moscow, as BuzzFeed reported on Thursday, Bernstein said Sunday on CNN’s “Reliable Sources.”

“We don’t know where we are with this story right now,” but it might “shake out” in February if Cohen testifies before Congress, he added.

But, Bernstein noted, “I think you also need to look at what the pattern has been” in the Russia story. “It is the press that has been accurate throughout this,” he said, adding that “the president has been telling one untruth after another.”

“We have a president of the United States who lies ... serially, routinely, compulsively, such as never has happened in our modern history of the presidency,” Bernstein said.

Special counsel Robert Mueller’s office issued a rare statement Friday saying that BuzzFeed’s “description of specific statements” and the “characterization” of documents and testimony obtained by Mueller were “not accurate.

Bernstein noted that it’s still unclear if that means the substance of the story is untrue or if the statement refers to “how the special prosecutor came to know such a thing if indeed that is what happened.”

He noted that he and Bob Woodward made an embarrassing mistake that challenged the credibility of their reporting on Watergate. They reported in The Washington Post that President Richard Nixon’s chief of staff directed the payment of hundreds of thousands of dollars to the Watergate burglars. They cited grand jury testimony that in fact did not exist, which the Nixon administration used to slam all of the Post’s Watergate coverage. But the substance of the story turned out to be true.

Bernstein cautioned that “we need to wait for the Mueller report.” But “in the meantime, from available sources, including filings by Mueller ... we have established ... that the president of the United States, his family members, people closest to him in the campaign have lied at every turn in almost everything concerning Russia.”

Watch the rest of Bernstein’s interview in the video above.