Sen. Richard Burr, the chairman of the Senate Intelligence Committee, pushed back Thursday on ex-CIA Director John Brennan's claim that President Trump colluded with the Russians, warning that it could be an "intelligence breach."

The challenge by Burr comes as some GOP allies say Trump abruptly revoking Brennan's security clearance this week is no big deal, while Democrats and allies of Brennan suggest it could set it a dangerous precedent for ex-officials who have been vocal critics of the president.

The White House announced on Wednesday that Trump revoked Brennan's security clearance, after which Brennan accused the president of attempting to "suppress freedom of speech & punish critics." In an interview with the New York Times published Thursday morning, Brennan, who was CIA director under former President Barack Obama, said there is no doubt Trump colluded with Russia during the 2016 presidential election despite his repeated denials.

“Mr. Trump’s claims of no collusion are, in a word, hogwash,” Brennan wrote in an opinion piece published Thursday for the Times.

"Director Brennan's recent statements purport to know as fact that the Trump campaign colluded with a foreign power," Burr said in a statement Thursday afternoon. "If Director Brennan's statement is based on intelligence he received while still leading the CIA, why didn't he include it in the Intelligence Community Assessment released in 2017? If his statement is based on intelligence he has seen since leaving office, it constitutes an intelligence breach."

Burr was referring to the January 2017 intelligence community assessment which determined Russia was behind an effort to interfere in the 2016 election which got Trump elected to White House. The North Carolina Republican went on to say Brennan using the media as an outlet to lash out at Trump may not have been a wise choice.

"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," Burr continued, alluding to special counsel Robert Mueller, who is leading the federal Russia investigation. "If, however, Director Brennan's statement is purely political and based on conjecture, the president has full authority to revoke his scurrility clearance as head of the Executive Branch."

White House press secretary Sarah Sanders announced the move to revoke Brennan's security clearance on Wednesday and read a statement from Trump, citing the "risks posed by his erratic conduct and behavior" as the impetus for the move.

Brennan has been a vocal critic of the president, and he was the first in a list of ex- top officials-turned-Trump-critics whom the Trump administration has taken action against. Those individuals still under review include former FBI Director James Comey, former national security adviser Susan Rice, former Director of National Intelligence James Clapper, former Deputy FBI Director Andrew McCabe, and former Deputy Attorney General Bruce Ohr, who is still employed at the Justice Department.

After Brennan's security clearance was pulled, Sen. Mark Warner, Burr's Democratic counterpart on the Senate Intelligence Committee, warned that Trump revoking former CIA Director John Brennan's security clearance could set a precedent for taking similar action against Mueller.

"I worry whether this precedence will lead to the president trying to take away Mueller and his whole team's security clearances. This is clearly another effort to silence critics and not allow the Mueller investigation, and for that matter our Senate intelligence community investigation, to get to the bottom of this," Warner said.

Other ex-intelligence have since condemned the move too, including former NSA and CIA Director Michael Hayden, who warned that others could see their security clearance revoked as part of an effort to coerce former U.S. officials from speaking badly about Trump.

Allowing intelligence officials who retire to keep their security clearance is a common practice, security experts say, and are often used as consultants by current officials.

The Republican perception of Trump's move to revoke Brennan's security clearance has been mixed, with some simply shrugging it off. Sen. John Kennedy, R-La., told CNN that Brennan is a "butthead" who didn't need the security clearance.

Sen. Rand Paul, R-Ky., who lobbied for Brennan to lose his scrutiny clearance, applauded the move, saying he "participated in a shredding of constitutional rights, lied to Congress, and has been monetizing and making partisan political use of his clearance since his departure.”

Some Republicans did express concern that Trump's motive was purely political. “It just feels like a banana republic kind of step,” Sen. Bob Corker, R-Tenn., a frequent Trump critic, told reporters. “I don’t like it at all. It feels really vindictive.”