Washington (CNN) Former US intelligence chiefs expressed astonishment and condemnation Monday in response to President Donald Trump's comments at Monday's news conference with Russian President Vladimir Putin, with former CIA Director John Brennan calling the US President's performance "nothing short of treasonous."

Following his one-on-one meeting with Putin in Helsinki, Finland, Trump declined to endorse the US intelligence community's assessment that Russia interfered in the 2016 election over Putin's denial, saying the Russian President was "extremely strong and powerful" in his denial.

"Donald Trump's press conference performance in Helsinki rises to & exceeds the threshold of 'high crimes & misdemeanors.' It was nothing short of treasonous," Brennan, a frequent critic of Trump who served as CIA chief from 2013 through January 2017, tweeted during the event. "Not only were Trump's comments imbecilic, he is wholly in the pocket of Putin. Republican Patriots: Where are you???"

Donald Trump's press conference performance in Helsinki rises to & exceeds the threshold of "high crimes & misdemeanors." It was nothing short of treasonous. Not only were Trump's comments imbecilic, he is wholly in the pocket of Putin. Republican Patriots: Where are you??? — John O. Brennan (@JohnBrennan) July 16, 2018

Former Defense Secretary Chuck Hagel said Trump "failed America today," but stopped short of calling the President's behavior "treasonous."

"I would not have said it the way John (Brennan) said it. John can say it the way he wants to say it. But as to impeachment, we'll see how this plays out. That's a congressional responsibility and the Congress must do what they think is in the best interest of this country," Hagel told CNN's Wolf Blitzer.

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