"Many of those who have answered the call of duty will spend this Christmas season far from home and separated from family," Bush said to a national television audience and a crowd gathered just south of the White House on a frigid night.
"We honor their sacrifice. We are proud of their service and that of their families. We will keep them close to our hearts and in our prayers," the president said.
With that, Bush led a short countdown as thousands of people rose to their feet on the Ellipse. The crowd roared when the 42-foot-tall (12.8-meter-tall) Blue Spruce came alive in color reds, blues, greens, and a golden star on top.
The president and first lady Laura Bush then joined Santa Claus, a children's choir and other entertainers for a rendition of "Jingle Bells" as the hourlong program came to end. The scene drew members of the Cabinet and Congress, along with invited guests of the White House and plenty of school-age children with parents.
Every president has presided over the tree lighting since Calvin Coolidge in 1923.
There is no shortage of Christmas pageantry inside the White House, a couple of hundred yards (meters) away, reports AP.
In the Blue Room, the White House Christmas Tree is an 18-foot (5.5-meter) Douglas fir, adorned with glass ornaments, red satin bows and cotton snow.
Ten-foot-tall (3-meter-tall) Nutcrackers stand at the entrance to the East Wing. Ribbons, garland and wreaths are everywhere. At the end of the ground floor corridor, there are even ivy topiaries shaped like the pets of the president and the first lady: Scottish terriers Barney and Miss Beazley and the First Cat, Willie.
Roughly 45,000 people will tour the White House during the holidays.
For those invited to a series of private parties hosted by the president and the first lady, the catering demands add up. The White House expects to go through 2,100 pounds (952.6 kilos) of sweet potatoes, 4,000 pounds (1,814.4 kilos) of shrimp, 4,000 pounds (1,814.4 kilos) of crab claws, plus 100 cases of asparagus, 15,000 chocolate truffles and 20,000 cookies.