Biden mixes up Taylor Swift and Britney Spears as he pardons turkeys Liberty and Bell: President jokes about being '60' on his 81st birthday - then confuses pop stars performing in Brazil

Joe Biden mixed up Taylor Swift and Britney Spears as he went off script while pardoning two turkeys at the White House.

The president, who is celebrating his 81st birthday today, also joked about his age, saying he was really only turning 60.

He undertook the traditional presidential duty of pardoning turkeys for Thanksgiving, this year sparing a pair named Liberty and Bell.

Biden said the birds had to 'beat some tough odds and competition' to be with him on the White House lawn.

He went on: 'You could say even harder than getting a ticket to the Renaissance tour...or, or, or...Britney's tour...she's down in...it's kind of warm in Brazil right now.'

The Renaissance tour was Beyonce's world tour that ended last month.

Britney Spears has not toured for several years and is currently not in Brazil.

The president appeared to mean Taylor Swift, who is currently performing a series of shows on her 'Eras Tour' in Brazil.

On Friday, a 23-year-old fan died amid extreme temperatures at a Taylor Swift concert in Rio de Janeiro, leading the superstar to postpone her Saturday night show there.

The gaffe by Biden was the latest drawing attention his age, with polls showing him losing ground to Republican frontrunner Donald Trump among under-35s.

Polls show three quarters of Americans believe Biden is too old to be effective for four more years.

At the turkey pardoning Biden made light of his age.

He said: 'By the way, it's my birthday today...I just want you to know it's difficult turning 60.'

The president added: 'This is the 76th anniversary of this event. I want you to know I wasn't there...'

When presented with one of the turkeys to pardon he said: 'That's a big bird man. I'm impressed. I hereby pardon, liberty and Bell. Congratulations birds.'

Biden said he wanted to 'conclude on a serious note about why we have Thanksgiving in the first place'.

He said it was 'to remind ourselves, and we sometimes forget this, how we have so much to be thankful for as a nation.

'Let's remind ourselves that we're blessed to live in the greatest nation on the face of the Earth.'

The president also paid tribute to former First Lady Rosalynn Carter who passed away at the weekend.

The turkey pardoning event took place on the White House South Lawn this year instead of the Rose Garden.

It marks the unofficial start of the holiday season in Washington.

Steve Lykken, chairman of the National Turkey Federation, said: 'We think that's a great way to kick off the holiday season and really, really a fun honor,"

The turkeys were brought by road from in a black Cadillac Escalade from their home at the Jennie-O company in Minnesota.

On Sunday night they were taken to the Willard Intercontinental, a luxury hotel close to the White House, and given a suite in which the floor had ben covered with plastic sheeting.

The checked into a suite there on Saturday following their red-carpet arrival in the U.S. capital after a dayslong road trip from Minnesota in a black Cadillac Escalade.

Ahead of their big day they were played music - including Taylor Swift songs - to prepare them for the crowd at the White House.

Lykken said: 'They listened to all kinds of music to get ready for the crowds and people along the way.

'I can confirm they are, in fact, Swifties, and they do enjoy some Prince.'