For the fifth year in a row, President Bush on Thursday dedicated the lighting of the National Christmas tree to U.S. troops risking their lives far from home and loved ones.

"We ask for God to watch over our men and women in uniform who are serving overseas. Their families miss them, hold a seat open for them and pray for their safe return," Bush said. "Many of them are serving in distant lands tonight, but they are close to our hearts."

A moment later, the president and his wife, Laura, were aided by three local girls as they flicked the switch that illuminated the dazzling white lights and snowflakes that adorn the live, 40-foot Colorado blue spruce that stands permanently on the Ellipse just south of the White House.

Jackie, Melissa, and Jenna Kantor of nearby Bethesda, Md., were chosen to assist the president because they started a program called Project Backpack that assembles bags stuffed with school supplies for Gulf Coast children affected by Hurricane Katrina.

"We have a responsibility to help those in need," the president said after an hourlong outdoor variety show of Christmas songs and readings. "Acts of kindness toward others fulfill the spirit of the season."

Though the "Pageant of Peace" attended by thousands was festive, Bush noted soberly that "we approach Christmas in this time of war." Bush has never presided over a tree-lighting ceremony that has not included mentions of troops serving overseas in difficult missions, as his first Christmas as president came not long after the Sept. 11, 2001, terrorist attacks and Afghanistan campaign that followed, and the Iraq war began in 2003.

The tree will remain lighted and open for public viewing through December, and musical performances by volunteer choirs and dancers are scheduled nightly through Dec. 23.

The Bushes went from the Ellipse to the White House to kick off their holiday entertaining season. The first couple welcomed about 500 friends and supporters to a holiday reception on the lavishly decorated State Floor of the White House, press secretary Scott McClellan said.

Thursday's party guests were the first of 9,500 expected to attend almost nightly White House receptions through the holidays.