Following his brief speech, Biden, first lady Jill Biden, Vice President Kamala Harris and second gentleman Doug Emhoff walked out to the South Portico at the White House where candles were lit and displayed on the steps for the moment of silence.

Earlier, the National Cathedral rang its bells to honor the more than 500,000 Americans who died from the coronavirus.

"I received a letter from a daughter whose father died of COVID-19 on Easter Sunday last year," Biden said before the ceremony. "She and her children, his grandchildren, enter Lent this season, a season of reflection and renewal, with heavy hearts. Unable to properly mourn, she asked me in the letter, what was our loss among so many others? Well, that's what has been so cruel."

"So many of the rituals that help us cope, that help us honor those we loved, haven't been available to us. The final rites, with family gathered around, the proper home going, showered with stories and love, tribal leaders passing out the final traditions of sacred cultures on sacred lands," he continued. "As a nation, we cannot and we must not let this go on. That's why the day before my inauguration ... I said, 'to heal -- to heal, we must remember.' I know it's hard. I promise you, I know it's hard. I remember. But that's how you heal. You have to remember."

In remarks ahead of a candlelight ceremony, Biden addressed the nation.

"Today we mark a truly grim, heartbreaking milestone: 500,071 dead," Biden said.

"That's more lives lost to this virus than any other nation on Earth. But as we acknowledge the scale of this mass death in America, remember each person and the life they lived," he continued.

"We often hear of people described as 'ordinary Americans.' There's no such thing. There's nothing ordinary about them. The people we lost were extraordinary. They spanned generations. Born in America, immigrated to America, but just like that, so many of them took their final breath alone in America," Biden said. "As a nation, we can't accept such a cruel fate. While we've been fighting this pandemic for so long, we have to resist becoming numb to the sorrow. We have to resist viewing each life as a statistic or a blur or on the news. We must do so to honor the dead, but equally important, care for the living, those they left behind -- for the loved ones left behind."

The House is one step closer to sending the White House's $1.9 trillion COVID-19 relief package to the Senate after the bill advanced through the House Budget Committee Monday. The committee favorably reported the proposal to the full House in a near-party line 19-16 vote.

"We are in a race against time," House Budget Committee Chairman John Yarmuth, D-Ky., said. "Aggressive, bold action is needed before our nation is more deeply and permanently scarred by the human and economic costs of inaction."

Republicans decried the price tag for the package and accused Democrats of using the pandemic as an excuse to pass key agenda items, including the $15 an hour minimum wage increase.

-ABC News' Benjamin Siegel

The president issued a proclamation following the U.S. recording 500,000 deaths from COVID-19 and he noted that this means more Americans have now died from the virus in one year, compared to in World War I, World War II and the Vietnam War combined.

At 6 p.m., Biden will deliver remarks on the more than 500,000 lives lost to COVID-19 and then he, Harris and their spouses will observe a moment of silence and hold a candle-lighting ceremony at sundown.

In addition, Biden ordered flags lowered to half-staff on federal property for the next five days.

Earlier Monday, White House press secretary Jen Psaki told ABC New Chief White House Correspondent Cecilia Vega that the administration is still working to undo the "inherited" circumstances of the pandemic, taking a swipe at the Trump administration.

"Our focus is on building out of the hole that we inherited," Psaki said.

-ABC News' Sarah Kolinovsky and Justin Gomez

Rep. Ted Budd, R-N.C., had a message for Democrats last summer about their proxy voting system set up during the pandemic: it was an "unconstitutional scheme."

"If you use Nancy Pelosi's proxy to skip work, you shouldn't get paid. It's as simple as that," he said in a June 30 Facebook video introducing his new bill withholding member pay for proxy voting.

Budd wasn't alone: A handful of House Republicans previously critical of the proxy vote system submitted letters to have colleagues vote for them, while they were scheduled to appear at CPAC.

Freshman Rep. Madison Cawthorn, R-N.C., tweeted last summer that leaders "show up no matter how uncertain the times are," and that Democrats were "cowards for hiding" and proxy voting.

He was also in Orlando on Friday, telling conservatives activists, "If we sit on the sidelines, we will not have a country to inherit."

"If we do not get involved and say that it is our duty to make sure that our country is responsible, that our country doesn't take away our liberties, then my friends, we will lose this nation," Cawthorn said.

Others Republicans scheduled to appear at CPAC on Friday who also planned to vote by proxy included Reps. Greg Steube of Florida, Virginia Foxx of North Carolina, and Matt Gaetz of Florida, who was one of the first Republicans to support proxy voting.

Curtis Kalin, a spokesman for Budd, said the congressman still opposes proxy voting, and will donate his salary for the days he used the system to a restaurant relief fund, given his bill last year, "The No Pay for Proxy Voting Act."

The Republicans who attended CPAC aren't alone in their questionable use of the proxy voting system -- established by House Speaker Nancy Pelosi, D-Calif., last year to cut down member travel to Washington during the COVID-19 pandemic.

Last year, Rep. Greg Stanton, D-Ariz., was caught voting during a Transportation Committee hearing from a boat during a family trip to Utah. Stanton later apologized and said he "messed up." And several House Democrats voted by proxy last May in order to attend a SpaceX rocket launch in Florida.-ABC News' Benjamin Siegel