Former CIA Director John Brennan said special counsel Robert Mueller's public message Wednesday will escalate calls for impeaching President Trump.

“I think Bob Mueller’s public statement today is going to give momentum to those who want to move forward with impeachment hearings,” Brennan said on MSNBC. “I think there can be no doubt about Mr. Mueller’s message that the obstruction of justice issue is not resolved, and that there needs to be follow-up action on it.”

“I do think it’s going to give some additional momentum to them, whether or not they’re going to decide to do it,” the vocal Trump critic added. "This is not just a legal issue, it’s a political issue and obviously there are political considerations. I think the cry for impeachment is going to increase, and it’s going to be interesting to see how the White House and Mr. Trump reacts to a very clear, and I believe, very pointed statement by Bob Mueller.”

[Read more: Trump: 'Case is closed' on Mueller investigation]

In his first and only public address about his 22-month-long Russia investigation, Mueller refused to clear Trump of obstruction of justice even though he declined to make a determination on the matter. "As set forth in the report after that investigation, if we had had confidence that the president clearly did not commit a crime we would have said so," he said.

Citing longstanding Department of Justice policy, Mueller said charging a sitting president with a crime was not an option his team could consider and noted that charging Trump would be unconstitutional. Attorney General William Barr said he and former Deputy Attorney General Rod Rosenstein concluded there was insufficient evidence to establish a crime.

Some Democrats, including Sen. Kamala Harris, immediately seized on the speech by calling for impeachment. "What Robert Mueller basically did was return an impeachment referral. Now it is up to Congress to hold this president accountable. We need to start impeachment proceedings. It's our constitutional obligation," the 2020 candidate tweeted.

Rank-and-file Democrats in the House have been pressuring a resistant leadership to pursue impeachment proceedings against Trump, emboldened by the release of Mueller's report, which laid out 10 instances of possible obstruction of justice that his team examined. House Speaker Nancy Pelosi pushed back on these calls, saying last week that Trump "wants to be impeached" so that a Republican-controlled Senate can vindicate him. Instead, leadership prefers to focus on a bevy of investigations looking into Trump, his finances, and his inner circle.

Trump reacted to Mueller's address by insisting he is in the clear. "Nothing changes from the Mueller Report. There was insufficient evidence and therefore, in our Country, a person is innocent. The case is closed! Thank you," he tweeted.

[Related: Mueller resists public appearance before Congress: 'The report is my testimony']