Justin Bieber sings for Obama

Justin Bieber says US President Barack Obama is "one cool Prez".

The singer performed his festive hit Mistletoe at the 30th annual Christmas in Washington concert on Sunday.

This was the second time Justin has appeared at the event, which is held in front of the entire presidential family including President Obama, First Lady Michelle Obama and their daughters Sasha and Malia.

The first time was in 2009, when President Obama famously mispronounced the star's name.

However, the 17-year-old had a wonderful time this year and took to his Twitter account to share his excitement.

"Great night!" he wrote. "President Obama is one cool Prez. He told me he was 'chillin,' (sic)."

Conan O'Brien was on hand to host the event at the National Building Museum.

Justin was joined by acts including Cee Lo Green, Jennifer Hudson, The Band Perry and Nickelodeon star Victoria Justice who took turns singing holiday classics and some new hits.

Cee Lo opened the show with his own renditions of This Christmas and Santa Claus is Coming to Town.

But Jennifer stole the evening with her performance of Do You Hear What I Hear with the help of the American Family Choir. She was thrilled to be singing for the president once again.

"I don't know how many times I've sung for the president, but every time feels like the first time," she told USA Today.

To end the evening, Obama and his family gathered on stage with the artists to sing the carol Hark! the Herald Angels Sing.

The holiday concert special which supports the Children's National Medical Center will air on Friday on TNT.

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