Originally Published: 12 MAY 22 07:02 ET

Updated: 12 MAY 22 09:35 ET

By Sam Fossum and Nikki Carvajal, CNN

(CNN) -- The Biden administration on Thursday mourned 1 million American deaths from Covid-19, using the occasion to again urge Congress to pass additional funding to control the pandemic.

While other official tallies have placed the figure a bit short of that mark, the administration marked the moment during the second Covid summit, reflecting on the pandemic's devastation on the nation after more than two years.

"One million empty chairs around the dinner table. Each an irreplaceable loss. Each leaving behind a family, a community, and a nation forever changed because of this pandemic," President Joe Biden said in a statement, adding that he and first lady Jill Biden "pray for each of them."

"As a nation, we must not grow numb to such sorrow. To heal, we must remember. We must remain vigilant against this pandemic and do everything we can to save as many lives as possible, as we have with more testing, vaccines, and treatments than ever before," Biden wrote. "It's critical that Congress sustain these resources in the coming months."

Biden ordered flags to be flown at half-staff to mark the occasion.

The White House on Thursday is hosting a virtual Global Covid-19 Summit, which is aimed at "redoubling" efforts to control Covid-19 and preparing the world for future variants of the coronavirus or the next deadly pandemic, two senior administration officials said.

The event, which is also co-hosted by Germany, Indonesia, Senegal and Belize, will call for countries to invest in the new Global Pandemic Preparedness and Health Security fund at the World Bank, and the United States will be announcing that its pledge will increase to $450 million, up from the initially promised amount of $250 million. The summit will also highlight an additional $3.1 billion in new funding commitments from countries around the world to combat Covid-19.

But as Biden, Vice President Kamala Harris and other Cabinet-level officials take part in Thursday summit, which will urge other wealthy countries to ramp up their coronavirus relief efforts in support of poorer countries, the Biden administration's efforts to secure further funding from Congress to support coronavirus relief efforts will be front and center.

Administration officials on Thursday will issue a "loud call" to Congress to act and take "urgent action, not empty words," one senior official said.

"If the US is to remain a leader -- protecting Americans and the world from dangerous disease threats -- we need Congress to act now to provide more funding for the Covid response," the second official added.

In addition to the summit's two overarching goals, there are three key priorities that will guide Thursday's gathering: preventing complacency on Covid-19, preventing deaths from the pandemic, and preventing future variants and pandemics -- with one official noting it is "not a matter of if, but when."

This will be the second global Covid-19 summit the White House has hosted, following one in September.

Secretary of State Antony Blinken, US Ambassador to the United Nations Linda Thomas-Greenfield, Secretary of Health and Human Services Xavier Becerra, USAID Administrator Samantha Power, deputy national security adviser Daleep Singh and White House Covid response coordinator Dr. Ashish Jha will also take part in Thursday's summit.