Former CIA Director John Brennan said Wednesday that President Trump's decision to revoke his security clearance is part of a broader effort by the administration to silence Trump's political adversaries.

"This action is part of a broader effort by Mr. Trump to suppress freedom of speech & punish critics. It should gravely worry all Americans, including intelligence professionals, about the cost of speaking out. My principles are worth far more than clearances. I will not relent," Brennan tweeted.

[Opinion: Trump is wrong to suspend John Brennan's clearance]



This action is part of a broader effort by Mr. Trump to suppress freedom of speech & punish critics. It should gravely worry all Americans, including intelligence professionals, about the cost of speaking out. My principles are worth far more than clearances. I will not relent. https://t.co/TNzOxhP9ux — John O. Brennan (@JohnBrennan) August 15, 2018



Brennan told MSNBC Wednesday afternoon that he plans to "continue to speak out" against Trump. He also said he was completely caught off guard by Sanders' announcement.

"I was called by a friend of an associate when Sarah Huckabee Sanders was giving that statement. I had no knowledge ... The first I had heard about was when I had turned on the television ... I have not heard anything from anyone in the government since then or before then," Brennan told MSNBC.

When asked why the president might have revoked his security clearance and is considering revoking other intelligence officials' clearances, Brennan said that he believes the president fears the types of criticism that he and other officials have expressed since the president took office.

"He may very well have a guilty conscience for things he has done in the past," Brennan told MSNBC. "I don't know what he may be concerned about as far as what may be divulged in this investigation."

Pressed on whether Brennan has any idea what Mueller is pursuing in his ongoing investigation into Russian interference in the 2016 presidential election, the former CIA director said he doesn't know, but believes the president is working to cover something up.

"I don't know what Bob Mueller is pursuing," Brennan said, adding that Mueller and his team will continue to look for "evidence of any criminal wrongdoing."

"Clearly, I think Mr. trump is more and more desperate, more and more concerned ... I know some things that the Russians were involved in. I certainly don't know all the things Mr. Trump has been involved in over the years," Brennan told MSNBC. "Clearly, his actions are those of somebody who is seeking to prevent the light of day being shed on his past."

White House press secretary Sarah Sanders announced Wednesday afternoon that President Donald Trump revoked Brennan's security clearance, citing "erratic behavior" that disqualified him from retaining his access to classified information.

"As the head of the executive branch and the commander in chief, I have a unique constitutional responsibility to protect the nation’s classified information, including by controlling access to it," Sanders said in a statement from the president Wednesday. "Today, in fulfilling the responsibility, I have decided to revoke the security clearance of John Brennan, the former director of the Central Intelligence Agency."