Obama starts singalong as he turns on Christmas lights

US President Barack Obama starts a singalong as he and his family flip the switch at the 90th annual lighting of the National Christmas Tree in America.

Daughters Malia, 14, and 11-year-old Sasha joined wife Michelle with their President dad as they sang Santa Claus is Coming to Town.

Actor Neil Patrick Harris hosted the event, which was attended by around 17,000 people.

Watch the video below: