On the margins of a White House photo session, US President Joe Biden was overheard on a live microphone Monday calling a Fox News journalist a “dumb son of a bitch.”

As journalists exited the room following the presentation, a Fox News reporter, a favourite of conservatives, inquired whether inflation is a political liability.

The Democratic leader began by deadpanning, apparently unaware that his microphone was still on: “It’s a fantastic asset. Inflation will rise further.”

Then he murmured, “What a foolish son of a bitch,” before looking down briefly.

A pool reporter in the room at the time stated that he couldn’t hear what Biden said because of the commotion.

He did, however, say that he would “direct your attention to footage of the event if you are interested how the president truly feels about being asked about inflation by Fox’s Peter Doocy.”

In a subsequent Fox interview, Doocy dismissed the slur.

“Yeah, nobody has fact-checked him yet and claimed it’s not true,” he joked.