ARLINGTON, Va. — President Barack Obama carried out the traditional Veterans Day role Wednesday, then made a surprise visit to a part of Arlington National Cemetery reserved for troops killed in Iraq and Afghanistan, walking among the grave sites and talking to mourners.

In his brief speech after a wreath-laying at the Tomb of the Unknowns, Obama paid fond tribute to the determination of the U.S. military, from those who served generations ago to today's troops fighting in Afghanistan, Iraq and missions around the world.

"To all of them — to our veterans, to the fallen and to their families — there is no tribute, no commemoration, no praise that can truly match the magnitude of your service and your sacrifice," he said.

Obama pledged he would do right by all veterans and families, saying: "America will not let you down."

The president spoke one day after somberly honoring the victims of a shooting rampage at Fort Hood, Texas. His first Veterans Day as president comes as Obama is on the cusp of announcing a revamped war strategy in Afghanistan that is expected to include sending thousands more troops into that war zone.

After his comments, Obama and first lady Michelle Obama spent some time in the section of the cemetery where fallen troops from the Iraq and Afghanistan wars are buried. The Obamas surprised family members who were there to pay their respects and spent some time talking to them.

Earlier at this national burial ground for war heroes, Obama, wearing a black raincoat, placed a flower-laced wreath on a stand and stood over it silently for several moments at the site of the Tomb of the Unknowns. He placed his hand on his heart as a bugler played taps.