WASHINGTON (AP) — President Barack Obama speaks at a World AIDS Day event Thursday and also helps light the National Christmas Tree.

At the AIDS ceremony, Obama will be joined, by video hookup, with former presidents Bill Clinton and George W. Bush. They'll note that a lot of progress has been made against the disease, but a lot still needs to be done.

The event, which is hosted by the ONE Campaign and (RED), will be held at George Washington University.

In the evening, the first family officially kicks off the Christmas season with the lighting of the National Christmas Tree on the Ellipse. The president will make a few remarks.