President Donald Trump and his wife Melania have lit the National Christmas Tree in the park behind the White House.

Mrs. Trump hit the switch to light the tree after her husband did a countdown from 10, urging audience members to join in.

Trump declared: ``Merry Christmas, everybody. We just have to say it all together: Merry, merry Christmas.''

The first lighting took place on Christmas Eve in 1923, when President Calvin Coolidge lit a Christmas tree in front of 3,000 spectators.

The National Christmas Tree is a living Colorado blue spruce and is surrounded by 56 smaller trees featuring ornaments from every state and territory and the District of Columbia.

Scroll below for photos of the 2018 lighting ceremony.