James Comey and Jeff Sessions. Yuri Gripas/Reuters Former FBI Director James Comey said during his blockbuster testimony on Thursday that there were "facts" the public didn't yet know about why Attorney General Jeff Sessions deemed it necessary to recuse himself from matters involving the bureau's Russia investigation.

Sessions recused himself in early March after it became public that he did not mention during his confirmation hearings that he had met with Russian Ambassador Sergey Kislyak during the campaign.

Comey said the FBI was "also aware of facts" about Sessions that made it necessary for him to recuse himself that Comey said he couldn't "disclose in an open setting."

Earlier this week, multiple outlets reported that the deteriorating relationship between Sessions and President Donald Trump was a result of Sessions' recusal, which was at the center of Trump's monthslong frustrations. ABC News reported on Tuesday that Sessions recently suggested he could resign amid the increasing "friction between the two."

"Our judgment, as I recall, was that he was very close to and inevitably going to recuse himself for a variety of reasons," Comey said. "We also were aware of facts that I can't discuss in an open setting that would make his continued engagement in a Russia-related investigation problematic.

"And so we were convinced — and, in fact, I think we already heard that the career people were recommending he recuse himself — that he was going to be in contact with Russia-related matters much longer," he continued. "And that turned out to be the case."

Watch Comey's comments: