Joe Biden was hosting a traditional festive phone call with children tracking Father Christmas' sleigh when their father told the president "Let's go Brandon".

Mr Biden, apparently unaware of the insult, responded saying: "Let's go Brandon, I agree", before the call was disconnected.

The coded jibe has been popularised by Conservatives after a television journalist told Nascar driver Brandon Brown live on air that a crowd chanting "F*** Joe Biden" were actually saying "Let's go Brandon".

The slogan has since become a viral meme that has even been worn on a face mask by a Republican member of the US House of Representatives.

The incident occurred while the president and his wife took calls for the North American Aerospace Defence Command (NORAD) tracker, which monitors Father Christmas' journey across the globe each Christmas.

It's part of an annual tradition that began in the 1950s when a child accidentally called an on-duty US military commander while trying to contact Father Christmas.

NORAD now hosts a volunteer hotline that children can dial for updates as Father Christmas makes his annual voyage to households around the world.

Like many other presidents in the past, Mr Biden was drafted in on Christmas Eve to take phone calls from children contacting NORAD's switchboard.

The president had already taken three phone calls when he spoke with a family from Oregon: Griffin, 11, Hunter, three, Piper, four, Penelope, two, and their father, Jared.

The conversation initially appeared unremarkable, with each of the children telling Mr Biden and his wife Jill that they hope to receive a Barbie, a piano and a Nintendo Switch for their Christmas presents.

At the end of the call, Mr Biden told Jared: "I hope you have a wonderful Christmas."

The father replied: "Yeah, I hope you guys have a wonderful Christmas as well. Merry Christmas and let's go Brandon."

Much about the exchange was not immediately clear, including what the caller intended, why Mr Biden repeated the slogan and whether either knew the origin of the phrase.

The White House did not respond to requests seeking comment.