Former FBI Director James Comey James Brien ComeyDemocrats fear Russia interference could spoil bid to retake Senate Book: FBI sex crimes investigator helped trigger October 2016 public probe of Clinton emails Trump jabs at FBI director over testimony on Russia, antifa MORE said on Sunday that he did not believe President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE was aware of the explosive allegations made against him in the "Steele dossier."

Comey briefed Trump on the unverified document, compiled by former British intelligence officer Christopher Steele, last year.

"When you told him the contents of the Steele dossier, did you get the impression it was the first time he'd ever heard those allegations?" NBC's Chuck Todd asked Comey on "Meet the Press."

"Yes," Comey said, "And I didn't give him the briefing on the whole Steele dossier. My assignment was to brief him on a small part of it that was salacious and personal. And my sense was, I didn't get a sense that he knew about those," he continued.

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The document purports to show Trump's ties to Russia.

Comey explained his reasoning for telling the president about salacious parts detailed in the dossier.

"We thought it was important that he knew — and I say, 'we,' meaning all the intelligence chiefs that put together the intelligence community assessment — because we knew, and we don't want to be holding that back from the new president," Comey said.

"The FBI's role is counterintelligence. We do a defensive briefing, whether or not something's true, just to let the person who might be the target of a leverage effort, of an effort by an adversary to gain advantage over him, know that we have this information," he said.

Comey revealed in memos that Trump considered bringing a lawsuit against Steele, denying the document's claim that he was involved with Russian prostitutes.