The White House said President Donald Trump has "begun the mechanism to remove security clearances" from former national security and intelligence officials who have been critical of his presidency - but later said Trump is still exploring the idea.
"He's also looking into the clearances of Comey, Clapper, Hayden, Rice, and McCabe", she said.
Brennan, Clapper, Hayden and Rice have all been critical of Trump's foreign policy, including the US president's embrace of Russian President Vladimir at a summit in Helsinki.
Trump has been seething over criticism of his Helsinki summit last week with Russian leader Vladimir Putin and public doubts Trump expressed about USA intelligence findings that Russia interfered with the 2016 presidential election.
Some of the former officials on the list have made "baseless accusations of improper contact with Russia" that "provides inappropriate legitimacy to accusations with zero evidence", Sanders said.
Melissa Schwartz, a spokeswoman for McCabe, said Sanders was mistaken about his status - she said McCabe's clearance was already deactivated when he was sacked earlier this year.
Gidley told a reporter, "What I meant to say was it's being looked at". "I'm not aware of any plans for that at this point", she said.
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Sen. Rand Paul (R-Ky.) said Monday Trump should revoke Brennan's clearance, but Sanders said Trump wants to go further. "This is a political attack on career national security officials who have honorably served their country for decades under both Republicans and Democrats in an effort to distract from [special counsel Robert Mueller's] investigation".
"They've politicized and in some cases monetized their public service", Sanders said during a press briefing.
Shortly after the call, former Clinton counter-terror adviser Richard Clarke said on ABC News that the plot "never came close because they had insider information, insider control" - the detail allegedly disclosed by Brennan.
Paul kept true to his stance on revoking Brennan's security clearance in an interview with Martha MacCallum of Fox News on Monday evening, saying he was "concerned" about Brennan having privileges due to his past conduct in the Central Intelligence Agency.
"I don't go back for classified briefings", Hayden said in a tweet.
Comey's lawyer, David Kelley, said the ex-FBI director "was read out of his security clearance not long after he left the FBI" in mid-2017, after Trump fired him.
But they agreed that a president asking to revoke the clearance of a political critic would be unprecedented.
Former CIA directors typically hold on to their clearance for several years after leaving office in part so that they can share insights with current directors.
At least two of the former officials, who have served in both Democratic and Republican administrations, do not now have security clearances: Comey and McCabe.