President Trump's ongoing battle with John Brennan escalated over the weekend, when the former CIA Director threatened to sue the Trump administration after his security clearance was stripped.

In a Sunday interview with NBC's Chuck Todd, Brennan blasted Trump for what he calls an "egregious abuse of power and authority," adding that he's "been contacted by a number of lawyers" who have advised him on legal options - including the possibility of suing the Trump administration for an injunction to stop more clearances from being revoked.

On Monday morning, President Trump hit back - tweeting "I hope John Brennan, the worst CIA Director in our country’s history, brings a lawsuit. It will then be very easy to get all of his records, texts, emails and documents to show not only the poor job he did, but how he was involved with the Mueller Rigged Witch Hunt. He won’t sue!"

I hope John Brennan, the worst CIA Director in our country’s history, brings a lawsuit. It will then be very easy to get all of his records, texts, emails and documents to show not only the poor job he did, but how he was involved with the Mueller Rigged Witch Hunt. He won’t sue! — Donald J. Trump (@realDonaldTrump) August 20, 2018

In a follow-up tweet, Trump said "Everybody wants to keep their Security Clearance, it’s worth great prestige and big dollars, even board seats, and that is why certain people are coming forward to protect Brennan. It certainly isn’t because of the good job he did! He is a political “hack.”"

Everybody wants to keep their Security Clearance, it’s worth great prestige and big dollars, even board seats, and that is why certain people are coming forward to protect Brennan. It certainly isn’t because of the good job he did! He is a political “hack.” — Donald J. Trump (@realDonaldTrump) August 20, 2018

On Wednesday, the White House announced that it was revoking Brennan's clearance, and that the status of other former officials was under review. Critics have accused the White House of trying to silence political opponents. "Trump says he is reviewing security clearances for nine other individuals: James Clapper, James Comey, Michael Hayden, Sally Yates, Susan Rice, Andrew McCabe, Peter Strzok, Lisa Page and Bruce Ohr. Some have been publicly critical of the president, while others are linked to special counsel Robert Mueller’s investigation into Russian election interference," wrote the Washington Post on Wednesday.

Blowback

Brennan has taken flack over his recent outbursts, including accusing President Trump of treason (which MSNBC's Rachel Maddow of all people took him to task over).

Former Director of National Intelligence James Clapper threw former CIA Director John Brennan under the bus on Sunday, telling CNN's "State of the Union" that "John and his rhetoric have become an issue in and of itself," adding "John is subtle like a freight train and he's gonna say what's on his mind."

Brennan's increasingly inflammatory commentary of late has also drawn the attention of Congressional GOP. On Thursday, Senate Intelligence Committee Chairman Richard Burr (R-NC) slammed Brennan for "purport[ing] to know, as fact, that the Trump campaign colluded with a foreign power."

"If his statement is based on intelligence he has seen since leaving office, it constitutes an intelligence breach. If he has some other personal knowledge of or evidence of collusion, it should be disclosed to the special counsel, not The New York Times," said Burr, who added that Trump had the "full authority" to rescind Brennan's clearance if the former CIA Director's statements were "purely politicial and based on conjecture."

On Friday's broadcast of MSNBC's "Rachel Maddow Show," Brennan defiantly stood behind his statement that Trump committed treason during the Helsinki summit with Russian President Vladimir Putin, which he called "nothing short of treasonous," before walking it back moments later.

"After Helsinki, you were stark, and even a little bit scary in your criticism of his behavior. You said it rose to treason," said Maddow.

"I said it was nothing short of treasonous," replied Brennan.

Maddow pushed back: "In this current controversy, that specific comment has been singled out by a number of people as a comment that maybe, by you, crossed the line, that was maybe –."

"Crossed what line?" Brennan responded.

Maddow said that she wasn't going to question Brennan's right to his remarks, though then asked "But do you stand by that consideration, and can you explain, can you elaborate what you mean by treasonous? It’s a very serious allegation."

Brennan answered: "I know what the Russians did in interfering in the election. I have 100% confidence in what they did. And for Mr. Trump to stand on that stage in Helsinki, with all the world’s eyes upon him, and to basically [say] he wouldn’t — he doesn’t understand why would the Russians interfere in the election. He’s given Mr. Putin and the Russians a pass time after time after time, and he keeps referring to this whole investigation as a witch hunt, as bogus, as — and to me, this was an attack against the foundational principle of our great republic, which is, the right of all Americans to choose their elected leaders. And for Mr. Trump to so cavalierly just dismiss that, yes, sometimes my Irish comes out, and — in my tweets, and I did say that it rises to and exceeds the level of high crimes and misdemeanors and is nothing short of treasonous. … I didn’t mean that he committed treason, but it was a term that I used, nothing short of treasonous."