Mr Brennan sought to reassure his "Irish brothers and sisters" that the U.S. is a strong country, but at the moment President Trump is "not upholding the image and reputation of what it means to be an American president. we're gonna get there but we have some rough waters to navigate", he said.
In his article on Thursday, Brennan claimed that the question was not if collusion took place, but whether it "constituted criminally liable conspiracy, whether obstruction of justice occurred to cover up any collusion or conspiracy, and how many members of "Trump Incorporated" had "attempted to defraud the government by laundering and concealing the movement of money into their pockets".
The Republican president said in a statement on Wednesday that he revoked Brennan's authorization for making what he called "unfounded and outrageous allegations" about his administration and was evaluating whether to strip clearances from other former top officials. "So, when I see Mr Trump in the oval office not conducting himself the way I think a president should I am going to speak out".
On his Twitter account, Trump reposted several comments supporting his revocation of Brennan's clearance, including one from Sean Hannity, a conservative Fox News television host.
"I call it the rigged witch hunt, [it] is a sham", Mr. Trump said in an interview.
Brennan, whose criticisms of Trump have escalated in recent months, wrote that the president was "desperate" to end the Russian Federation investigation.
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In his op-ed, Brennan characterised Trump's action as "politically motivated" and said it was "an attempt to scare into silence others who might dare to challenge him".
But she did not present any evidence that Brennan has actually ever mishandled classified information. Democratic lawmakers blasted the president's move as risky.
Press secretary Sarah Sanders accused the former officials of "politicizing agencies and departments that are specifically meant to not be political". Trump says he is reviewing security clearances for nine other individuals, including the eight pictured.
That directly contradicted a July 2017 statement from Trump Jr. - written with the consultation of the White House - that claimed the meeting had been primarily about adoption.
Trump said he does not trust "many of those people on that list" and does not think they are "good people". John Kennedy and Richard Shelby also deferred to presidential authority and focused on Brennan's faults. "I don't know why they give them security clearances anyway other than maybe a transition period", Shelby added.