With President Biden on Thursday set to convene his second Covid-19 summit, the White House has secured more than $3 billion in pledges from other countries and from philanthropies to fight the coronavirus pandemic — even as Congress has refused Mr. Biden’s request for additional emergency aid, senior Biden administration officials said.

The meeting is intended to reinvigorate the international response to the coronavirus crisis at a time when vaccination and testing rates are lagging, and as many nations are looking to put the pandemic behind them. Global health experts, officials and activists all said this week that the world needed to prepare for the possibility of another deadly variant.

“We’ve got to puncture the complacency about this, to make sure that people realize that if we don’t act, another variant is a possibility — and we don’t know how lethal it could be,” Gordon Brown, the former British prime minister who is now the World Health Organization’s ambassador for global health financing, said in an interview this week.

Mr. Biden has asked Congress for $22.5 billion — including $5 billion to fight the global pandemic — in emergency coronavirus aid, but the proposal is stuck on Capitol Hill, even as Congress hurries to approve $40 billion in emergency aid for Ukraine. Lawmakers are still struggling to figure out how to advance a pared-down $10 billion coronavirus package. A group of former heads of state, including Mr. Brown and Nobel laureates, called this week for Congress to fulfill Mr. Biden’s request.

The Biden administration will put forth a relatively small amount of money at the meeting: $200 million for a World Bank fund to prepare for future pandemics, and $20 million for pilot projects to bring coronavirus tests and treatments to poor nations, according to the senior officials, who spoke on the condition of anonymity to preview the gathering.

And the United States will also make a significant nonmonetary commitment: The National Institutes of Health has agreed to license its “stabilized spike protein technology” — a crucial component of Covid-19 vaccines and treatments — to companies through the Medicines Patent Pool. The organization is a global nonprofit backed by the World Health Organization that works to bring medicines to low- and middle-income nations at low cost.

The move is significant because it may lay the groundwork for other countries and companies to share their technologies, said Peter Maybarduk, who directs the global access to medicines program for Public Citizen, a consumer advocacy group.

While the United States has donated hundreds of millions of doses of vaccines to poor nations, it has been less aggressive about sharing technology.

“One of the terrible injustices and major impediments in this pandemic has been the exclusive control of critical medical technology,” Mr. Maybarduk said. By working with the Medicines Patent Pool, he said, the Biden administration would be “not only sharing doses, but sharing knowledge, on the view that sharing doses is charity and sharing knowledge is justice.”

Thursday’s gathering will unfold in a very different climate than the first Covid-19 summit, last September. The war in Ukraine is sapping energy and money from donor nations. The global vaccination campaign is stalled. Testing has dropped precipitously around the globe. Covid antiviral pills are now available in the United States, but remain scarce in low- and middle-income nations.

“We remain woefully behind in our efforts to vaccinate the world, with less than 13 percent of people in low-income countries having received two Covid shots,” Gayle Smith, who ran the State Department’s global Covid response under Mr. Biden and is now chief executive of the One Campaign, an advocacy organization, said on Wednesday. She added, “That the U.S. will not come to the table with any funds to offer tomorrow is deeply concerning.”

The summit is being hosted by Belize, Germany, Indonesia and Senegal. Mr. Biden will address the attendees in prerecorded remarks, and Vice President Kamala Harris will be the lead representative for the United States. Global health organizations, philanthropies and drug makers will also participate.

In preparing for the meeting, the senior administration officials said, the White House asked participants to make “important commitments of all types.” Countries including Canada, Korea, Spain and France would make financial commitments, they added. Some low-income nations will commit to accelerating their vaccination campaigns, and some drug makers will agree to consider setting lower prices for treatments.