Shortly after White House press secretary Sarah Huckabee Sanders announced that President Donald Trump is revoking John Brennan's security clearance, the former CIA director replied on Twitter:

"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."

>>MORE: Trump revoking former CIA director John Brennan's security clearance

Brennan later appeared in an MSNBC interview discussing the announcement.

"I think Mr. Trump is getting more and more concerned, more and more desperate and I would say more and more frightened, as there is closer and closer magnification of some of the things that those around him have been involved in. So I do think it's important that I continue to speak out," Brennan told MSNBC.

The announcement came weeks after Huckabee Sanders told reporters that Trump was looking into the process required to revoke security clearances from half a dozen former Obama administration officials.