ARLINGTON, Va. — President Donald Trump paid a Memorial Day tribute at Arlington National Cemetery to those who have fallen in battle or while protecting a nation forever thankful for their selfless service.

"We mourn alongside their families and we strive to be worthy of their sacrifice," the commander in chief told an audience of Cabinet members, military leaders, veterans and families assembled in the marble amphitheater near the Tomb of the Unknown Soldier.

WATCH: Taps is played at the Tomb of the Unknown Soldier at Arlington National Cemetery as the nation observes #MemorialDay. pic.twitter.com/5EqDOjmBfC — NBC News (@NBCNews) May 28, 2018

Trump said he came to the "sacred soil" of Arlington on Monday "to honor the lives and deeds of America's greatest heroes" — the men and women who laid down their lives so that others could be free.

Trump also laid a wreath at the tomb during his second Memorial Day trip to Arlington as president.

Before heading to the hallowed grounds across the Potomac River from the nation's capital, Trump tweeted that "those who died for our great country would be very happy and proud at how well our country is doing today."

In the tweet, the president veered from the somber to self-congratulatory, citing what he said was the "Best economy in decades, lowest unemployment numbers for Blacks and Hispanics EVER (& women in 18years) ..."

Happy Memorial Day! Those who died for our great country would be very happy and proud at how well our country is doing today. Best economy in decades, lowest unemployment numbers for Blacks and Hispanics EVER (& women in 18years), rebuilding our Military and so much more. Nice! — Donald J. Trump (@realDonaldTrump) May 28, 2018

He was criticized for his tone by a number of people, including the former chairman of the Joint Chiefs of Staff during the Obama administration, former Army Gen. Martin Dempsey, who tweeted, "This day, of all days of the year, should not be about any one of us."

John Kirby, a State Department spokesman in the Obama administration, called Trump's tweet "one of the most inappropriate, ignorant and tone-deaf things our Commander-in-Chief could have said on a day like today."

At Arlington, Trump said the heroes who died for America "rest in these hallowed fields, in cemeteries, battlefields and burial grounds near and far, and are drawn from the full tapestry of American life."

He said they came from "every generation, from towering cities and wind-swept prairies, from privilege and from poverty. They were generals and privates, captains and corporals of every race, color and of every creed, but they were all brothers and sisters in arms. And they were all united then, as they are united now, forever, by their undying love of our great country."

President Donald Trump speaks at the Memorial Amphitheater in Arlington National Cemetery on Memorial Day, Monday, May 28, 2018 in Arlington, Virginia. Alex Brandon / AP

Gen. Joseph Dunford, the current chairman of the Joint Chiefs of Staff, honored the more than a million Americans he said "gave their last full measure so we could live in freedom and raise our children in peace."

He also honored the families "they left behind and for whom every day is Memorial Day."

Those who fought and died for America, he said, "shared a commitment to something greater than themselves and they were people who understand what we have in this country is worth fighting for."

Those who attended the Memorial Day tribute included Trump's chief of staff, John Kelly, whose son, Marine 2nd Lt. Robert M. Kelly, was killed in November 2010 after he stepped on a land mine while on patrol in southern Afghanistan. He is buried at Arlington.