Jennifer Hudson has been spotted "pumping her fist" in approval while watching one of her own performances.

The American singer took to the stage at the Christmas in Washington show on Sunday. The event is staged annually to celebrate the festive season, with US President Barack Obama and his family in attendance this year.

It was taped to be aired on television later this week and Jennifer got into the spirit of things while watching it back on a recent flight.

"She was sitting with her assistant and watching her own performance [on a laptop]," a source told New York Post. "They both kept clapping, and Jennifer pumped her fist."

Jennifer headlined the show, with Justin Bieber also performing.

At the event she admitted she was nervous about singing in front of the president but felt honoured to be asked to take part in Christmas in Washington.

She explained she's "lost count" of the number of times she's taken to the stage in front of the Obama family. "But every time feels like the first time, and I get anxious," she added. "I always watch this at home on the TV and I'm like, Why aren't I there?'"

This year's show was the 30th anniversary of the event, which sees stars sing for the presidential family. Acts including Cee Lo Green, The Band Perry and Nickelodeon star Victoria Justice also took part, with 17-year-old Justin thrilled to be involved.

"Great night!" he wrote on Twitter afterwards. "President Obama is one cool Prez. He told me he was chillin,'.