ARLINGTON, Va. (AP) — President Joe Biden honored America’s war dead at Arlington National Cemetery on Memorial Day by laying a wreath at the hallowed burial ground and extolling the sacrifices of the fallen for the pursuit of democracy.

The president was joined on Monday by first lady Jill Biden, Vice President Kamala Harris and second gentleman Doug Emhoff in a somber ceremony at the Virginia cemetery's Tomb of the Unknown Soldier, which is dedicated to deceased service members whose remains have not been identified.

His face tight with emotion, Biden walked up to the wreath, cupping it in his hands in silent reflection and then making the sign of the cross. Later, he called on Americans to commemorate their fallen heroes by remembering their fight for the nation's ideals.

“This nation was built on an idea," Biden said in an address at Arlington. “We were built on an idea, the idea of liberty and opportunity for all. We’ve never fully realized that aspiration of our founders, but every generation has opened the door a little wider.”

He focused much of his speech on the importance of democracy, saying that it thrives when citizens can vote, when there is a free press and when there are equal rights for all.

“Generation after generation of American heroes are signed up to be part of the fight because they understand the truth that lives in every American heart: that liberation, opportunity, justice are far more likely to come to pass in a democracy than in an autocracy," Biden said.

The Bidens stopped by a row of gravestones after the ceremony, holding hands and speaking with a family whose relative died during World War II.

Other dignitaries at the Arlington event included Defense Secretary Lloyd Austin and Mark Milley, chairman of the Joint Chiefs of Staff.

On Sunday, Biden addressed a crowd of Gold Star military families and other veterans in a ceremony at War Memorial Plaza in New Castle, Delaware. Earlier in the day, he and other family members attended a memorial Mass for his son Beau Biden, a veteran who died of brain cancer six years ago to the day.