Sen. Bernie Sanders experienced a "technical issue" during a Friday interview on CNN after he made a joke that the news network was "fake news."

Appearing on "Outfront," the senator was asked to discuss reports that President Trump's national security adviser, Mike Flynn, had discussed sanctions on Russia with the country's ambassador the day before they were implemented by the Obama administration.

"This is a very troubling development," the senator said, adding that it "speaks to the broader issue of Russia's involvement in our elections" and "to the issue of President Trump being buddy-buddy" with Russian President Vladimir Putin, whom he called "a thug and a murderer."

CNN's Erin Burnett showed him a clip showing Trump saying he hasn't heard anything about new reports Friday contradicting Flynn's assertion that he did not speak with Russian Ambassador Sergey Kislyak about sanctions in December.

Asked if this is a problem, Sanders' response was: "Well I don't know. Maybe he was watching CNN fake news. What do you think?" he said, to which Burnett laughed. "It was a joke," he added.

Burnett replied, "I, I know it was a joke. I'm saying you don't buy what he said obviously" — but the senator did not appear to hear what she said.

"Erin?" Sanders asked. "Are we on?"

After a few moments and no resolution CNN cut to a commercial break. When the show returned, the connection with Sanders was re-established and Burnett apologized for the "technical issue" before moving on with the interview.

Trump has repeatedly criticized CNN, among other news outlets, for being "fake news."