ARLINGTON, Va. – President Bush paid tribute Monday to fallen U.S. troops, calling those who have died in Iraq and Afghanistan “a new generation of heroes” in a solemn Memorial Day visit to Arlington National Cemetery.

Speaking under overcast skies after laying a wreath of red, white and blue flowers at the Tomb of the Unknowns and meeting privately at the White House with the families of some troops killed in battle, Bush said that today’s fighting forces follow a rich tradition of American sacrifices throughout the nation’s history.

“Now, this hallow ground receives a new generation of heroes: men and women who gave their lives in places such as Kabul and Kandahar, Baghdad and Ramadi,” Bush said. “They believed in something larger than themselves. They fought for our country and our country unites to mourn them as one.”

As people across the country marked the day of remembrance, violence continued in Iraq where a suicide car bomber struck a busy commercial district in central Baghdad, killing at least 21 people and damaging a shrine revered by Sunnis and Shiites alike.

Speaking to the relatives of some of the more than 300,000 buried at the cemetery, Bush said, “Nothing said today will ease your pain. But each of you needs to know our country thanks you and we embrace you and we will never forget the terrible loss you have suffered.”

Bush said the freedoms that people enjoy in this country today “came at a great cost and they will survive only so long as there are those who are willing to protect them.”

The president said that even though the war in Iraq is in it’s fifth year, young men and women still volunteer for the U.S. armed forces. He said 174 Marines recently asked to have their enlistments extended.

“Those who serve are not fatalists or cynics,” he said. “They know that one day this war will end, as all wars do. Our duty is to ensure that its outcome justifies the sacrifices made by those who fought and died in it.

“From their deaths must come a world where the cruel dreams of tyrants are frustrated and foiled, where our nation is more secure from attack and where the gift of liberty is secured for millions who have never known it. This is our country’s calling,” Bush said. “It’s our country’s destiny.”

At least 3,452 members of the U.S. military have died since the beginning of the war in Iraq in March 2003, according to an Associated Press count.

At least 325 members of the U.S. military have died in Afghanistan, Pakistan and Uzbekistan as a result of the U.S. invasion of Afghanistan in late 2001, according to the Defense Department.