Updated

President-elect Joe Biden's pick for national security adviser, Jake Sullivan, acknowledged to the House Intelligence Committee that he had told reporters in 2016 that then-candidate Donald Trump's campaign could have ties to Russia.

Sullivan, who was Biden's national security adviser during the Obama administration, told members of the committee in a December 2017 interview that prior to the 2016 election he briefed reporters on his suspicions. Sullivan had been an adviser for Hillary Clinton's campaign and he said he met with reporters and producers from Fox, CNN, NBC, ABC and CBS.

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"[B]asically we sat with them and walked through what we understood to be the case from -- in terms of the DNC hack and leak, what we believed to be the case with respect to Russian involvement," Sullivan said, "and then what we thought the upshot of this was, which is you now have the start of a much more aggressive phase of an intelligence-led operation by foreign power, and there's likely to be more as we go forward, and people should really pay attention to this."

Sullivan went on to say he questioned why Russia would want to get involved. He first recognized that Vladimir Putin and Clinton "didn't have the greatest of relationships," but then outlined for reporters his reasons for suspecting Trump's campaign.

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Sullivan told members of Congress that Trump had been taking positions "that seemed to track almost exactly to Vladimir Putin's wish list," and so he told reporters about this, as well as ties to Russia and Trump campaign members Michael Flynn, Paul Manafort and Carter Page.

It was Page who was the target of a Foreign Intelligence Surveillance Act warrant, and was monitored by the FBI after leaving the Trump campaign. It was later discovered that a significant basis for the warrant was an unverified dossier compiled by Christopher Steele as opposition research for the Clinton campaign. It was also learned that Page had been working with the CIA, although that information was omitted from the warrant applications.

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Sullivan claimed during his House interview that he did not learn about the dossier until January 2017, but he admitted that he had heard about some of the information that it contained prior to then.

Fox News' Jacqui Heinrich contributed to this story.