US vice president JD Vance suffered an embarrassing blunder earlier this week after being caught poking fun at Donald Trump ahead of his Congress speech.

Waiting at the podium for the father-of-five’s arrival, the duo jointly began poking fun at Trump’s notoriously-lengthy speech-making skills, seemingly not realising that they’d mic’d up.

“By the way, I think the speech is going to be great,” the recording hears Vance say of Trump.

“But I don’t know how you do this for 90 minutes.”

Johnson then replies: “The hardest thing was doing it during Biden.”