Anderson Cooper was left speechless Monday night after Donald Trump became the first American president to “deny he provided aid and comfort to a dangerous adversary.”

The CNN host was referring to Trump’s declaration earlier in the day in which he denied having ever worked for the Russian government. 

Last week, an article by The New York Times indicated that the FBI had opened an investigation in 2017 into whether the president had been secretly working as an agent of the Kremlin. 

This was followed by another report from The Washington Post that said Trump had repeatedly sought to conceal details of his personal interactions with Putin. 

“It’s hard to be at a loss for words at this point,” Cooper said. “But there’s certainly plenty to say about all the contacts with Russians, all the lies about those contacts, the criminal charges and convictions and connection with the lying.”

Watch Cooper discuss Trump’s denial in the clip below.