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

One hundred and sixty chief executive officers sent an open letter to congressional leadership Wednesday, urging lawmakers to pass "immediate and large-scale federal legislation to address the health and economic crises brought on by the COVID-19 pandemic" on a bipartisan basis.

The letter asks Congress to "to authorize a stimulus and relief package along the lines of the Biden-Harris administration’s proposed American Rescue Plan," perhaps leaving some room for negotiation on what the final package will look like. But the letter makes clear that major business CEOs, including the heads of Morgan Stanley, Visa, United Airlines, BlackRock, Comcast and Google are pushing for relief on the scale of Biden's plan.

"The American Rescue Plan provides a framework for coordinated public-private efforts to overcome COVID-19 and to move forward with a new era of inclusive growth. The country’s business community is prepared to work with you to achieve these critical objectives," the letter says.

Just Tuesday, though, Sen. Mitt Romney, R-Utah, one of the few Senate Republicans who has shown willingness to buck his party, criticized the $1.9 trillion bill in a Wall Street Journal op-ed.

"The $1.9 trillion bill is a clunker. It would waste hundreds of billions of dollars, do nothing meaningful to get kids back to school, and enact policies that work against job creation. The Congressional Budget Office’s recent analysis of the plan found that more than a third of the proposed funding—$700 billion—wouldn’t be spent until 2022 or later, undermining the administration’s claim that the massive price tag is justified for urgent pandemic-related needs," Romney wrote.

Whether the pressure from big business will sway any Republicans in the Senate remains to be seen, but Wednesday morning's messaging from GOP lawmakers is pretty clear: They have no intentions of budging.

-ABC News' Sarah Kolinovsky