The announcement came the day after Michael Flynn reportedly invoked the fifth amendment, the right to not incriminate oneself, when subpoenaed by the Senate intelligence committee.
If there is no response from Flynn, the Senate Intelligence Committee may consider a contempt-of-Congress charge, said Chairman Richard Burr of North Carolina. Flynn had rejected the earlier subpoena for records as being so broad that providing them could make him vulnerable.
The panel will get two cracks at Brennan - the first in public at 10 a.m. ET and the second behind closed doors - nearly two months after his first appearance was dramatically canceled amid the chaos sparked by House intelligence Chairman Devin Nunes' clandestine White House trip.
"Frequently, individuals who go along a treasonous path do not even realize they are on that path until it gets to be a bit too late, and that's why my radar goes up early when I see certain things", Brennan said, explaining that he did not know whether the contacts between Trump team members and Russian Federation were "benign".
"I don't know whether such collusion existed", he said, later adding that as CIA director he did not "do evidence" and prosecute crimes, but rather collected intelligence. Only that, again in his words, "I saw interaction that in my mind raised questions of whether it was collusion.It was necessary to pull threads".
Brennan led the CIA during a critical period previous year when US intelligence agencies concluded that Russian Federation was not only attempting to disrupt the election but was actively seeking to defeat Democratic candidate Hillary Clinton and help elect Trump.
Beyond elections, Russian President Vladimir Putin will undoubtedly try to exploit political chaos and divisions in Washington, Brennan said.
Attorneys for Michael Flynn say that a daily "escalating public frenzy against him" and the Justice Department's appointment of a special counsel have created a legally risky environment for him to cooperate with a Senate investigation. Trump fired FBI Director James Comey earlier this month, prompting reports that the president tried to steer Comey away from Flynn and the Russian Federation investigation.
Pressed by committee members on what "evidence" he has of any collusion between the Trump campaign and Russian officials, Brennan said he has no evidence but has intelligence that he shared with the FBI, which used it as a basis for its investigation.
Coats told senators at a Senate hearing that it would be inappropriate to discuss private conversations he'd had with the president. That there's no truth in any of the media reports suggesting that the likes of Michael Flynn, Carter Page, Paul Manafort and Jared Kushner may have had interactions with the Russians that crossed a line. Cummings' letter came the same day Flynn declined to provide documents to the Senate Intelligence Committee, citing his Fifth Amendment protection from self-incrimination.
But Coats did not deny Trump had made such a request.
Former CIA Director John Brennan says Russia has a history of trying to "suborn individuals" and he anxious last summer about the number of contacts Russian officials were having with Americans.
As Brennan answers House lawmakers' questions in open and closed sessions, the Senate Armed Services Committee will hear from Trump's top intelligence official, Dan Coats, and the director of the Defense Intelligence Agency regarding national security threats.
The latest news most likely to hold the Capitol captive is word that Trump asked his own intelligence chiefs - Director of National Intelligence Dan Coats and National Security Agency Director Mike Rogers - to rebut Comey's then-public statement that the Federal Bureau of Investigation had opened a criminal probe into Russia's meddling in July of past year. He said he told Bortnikov that Russian interference "would destroy any near-term prospect of improvement" in the relationship between the US and Russia. He said the head of the FSB denied that Russian Federation was meddling, but said he would raise the issue with President Vladimir Putin.
Brennan also denounced classified intelligence leaks that continue to appear in the news media, including the nature of the Oval Office conversation Trump shared with the Russian foreign minister and ambassador to the US where he reportedly revealed highly classified intelligence reportedly shared with the U.S.by Israel.
"I have been asking Director Comey & others, from the beginning of my administration, to find the LEAKERS in the intelligence community", Trump tweeted.
Sen. Sheldon Whitehouse of Rhode Island, a member of the Senate Judiciary Committee, says the newspaper's report Monday is an indication that Trump is trying to impede the investigation.