President Joe Biden addressed the nation as the US marks 500,000 deaths from Covid, the most for any country in the world.
"As a nation, we can't accept such a cruel fate. We have to resist becoming numb to the sorrow," he said.
The president and vice-president, and their spouses, then observed a moment of silence outside the White House during a candle-lighting ceremony.
More than 28.1 million Americans have been infected - another global record.
"Today I ask all Americans to remember. Remember those we lost and remember those we left behind," he said, calling for Americans to fight Covid together.
President Biden ordered all flags on federal property to be lowered to half mast for the next five days.
At the White House, Mr Biden opened his speech by noting that the number of American deaths from Covid is higher than the death toll from World War I, World War II, and the Vietnam War combined.
"We often hear people described as ordinary Americans. There's no such thing," he said.
"There's nothing ordinary about them. The people we lost were extraordinary. They span generations. Born in America, emigrated to America."
"So many of them took their final breath alone in America," he continued.
He drew on his own experience with grief - his wife and daughter were killed in a car crash in 1972 and one of his son's died from brain cancer in 2015.
"For me, the way through sorrow and grief is to find purpose," he said in his live speech to the country.
Mr Biden's approach to the pandemic is different to his predecessor Donald Trump, who cast doubt on the impact of the deadly virus and was viewed as having politicised the wearing of masks and other measures to prevent the spread of the virus.
On 19 January, one day before Mr Biden took office, he held an event to mark 400,000 Americans dying of the disease.
Monday's event, marking the latest death toll, comes less than one month later.
Elsewhere in Washington, the bells at the National Cathedral tolled 500 times, once for every thousand Americans lost during the pandemic.
The number of Americans who have had the coronavirus is nearly double that of second-highest India (11 million) and Brazil (10.1 million). Brazil has recorded the second-largest death toll at 244,000 while Mexico is in third with 178,000.
"People decades from now are going to be talking about this as a terribly historic milestone in the history of this country, to have these many people to have died from a respiratory-borne infection," the Despite the improving figures, Americans' life expectancy has dropped by one full year due to the coronavirus, the US Centers for Disease Control and Prevention said last week. The change has been most acute among racial minorities, who have been disproportionally affected by the deadly virus.
Black men suffered the largest decline, with life expectancy dropping by three years between January and June 2020.
And Hispanic men saw a fall in life expectancy of 2.4 years during that period.nation's top immunologist, Dr Anthony Fauci, told CNN on Sunday.
"It is an astonishing number. A year ago I could not have imagined that half a million Americans would lose their lives to this disease," said Dr Ashish Jha, dean of the school of public health at Brown University.
"We have so much capability, so many resources in this country... this was all preventable and should not have happened. And yet here we are," he told BBC News on Monday. "And I think we have to reflect on all the ways in which our response went wrong."
At least 90,000 more Americans are expected to be killed by 1 June, according to a recent projection from the University of Washington's Institute for Health Metrics and Evaluation (IHME).
The IHME estimates that by late May, the virus will kill around 500 Americans per day - down from approximately 2,000 daily deaths now.
Hospital admission rates have fallen for 40 straight days, as approximately 1.6 million vaccinations are administered to Americans daily. But experts are still very concerned about the growing number of coronavirus variants in the country, which could spark new deadly outbreaks.
Despite the improving figures, Americans' life expectancy has dropped by one full year due to the coronavirus, the US Centers for Disease Control and Prevention said last week. The change has been most acute among racial minorities, who have been disproportionally affected by the deadly virus.
Black men suffered the largest decline, with life expectancy dropping by three years between January and June 2020.
And Hispanic men saw a fall in life expectancy of 2.4 years during that period. (BBC)
