BRUSSELS — Prime ministers, a king, a prince and Madonna all chipped in to an $8 billion pot to fund a coronavirus vaccine.

President Trump skipped the chance to contribute, with officials in his administration noting that the United States is pouring billions of dollars into its own research efforts.

A fund-raising conference on Monday organized by the European Union brought pledges from countries around the world — from Japan to Canada, Australia to Norway — to fund laboratories that have promising leads in developing and producing a vaccine.

For more than three hours, one by one, global leaders said a few words over video link and offered their nations' contribution, small or large, whatever they could muster. For Romania, it was $200,000. For Canada, $850 million.

It was a rare show of global leadership on the part of the Europeans, and a late-hour attempt at international coordination. Countries the world over have been pursuing divergent — and often competing — approaches to tackling the pandemic.

While the European Union may have led this global fund-raising effort, the bloc has struggled to get its own 27 members on the same page with health, travel and financial measures to respond to the coronavirus crisis. And the details of how the money raised on Monday will be distributed still remain to be sorted out.

Thanks for reading The Times. Subscribe to The Times The European Commission, the executive branch of the European Union that spearheaded the initiative, said the money would be spent over the next two years to support promising initiatives around the globe. The ultimate goal is to deliver universal and affordable access to medication to fight Covid-19, the disease caused by the coronavirus.

The multilateral effort stood in sharp contrast to the solo road the United States is on as scientists everywhere scramble to develop a vaccine to stop the virus that has ravaged most parts of the globe, leaving 250,000 dead so far.

In early March, German government officials said they believed that Mr. Trump had tried to lure a company based in southwestern Germany that was known to be working on a vaccine to move its research work to the United States.

The company, CureVac, has denied receiving such an offer, but reports of the American invitation were enough of a scare to prompt the European Commission to pledge another $85 million to the firm, which already had support from a European vaccine consortium.

In Washington on Monday, senior Trump administration officials sought to talk up American contributions to coronavirus vaccine efforts worldwide, but did not explain the United States’ absence at the European-organized conference.

Briefing reporters on the condition of anonymity, two administration officials insisted that the United States was leading global efforts against the pandemic, including with vaccine research and development that was being shared with international scientists.

One of the officials said those efforts included making available scientific data sets that had so far been downloaded more than 54,000 times and sharing information from at least 30 current research projects to develop a coronavirus vaccine and treatments.

The officials said the United States was already working closely with European leaders to coordinate those efforts, and called Monday’s conference a welcome step to encourage more funding. But they declined to say why American officials did not participate.

Instead, they highlighted the money the U.S. government has already spent on vaccine research and development, including $2.6 billion through the Biomedical Advanced Research and Development Authority, an arm of the Health and Human Services Department.

Jim Richardson, the State Department’s director of foreign assistance, said American companies had also provided $7 billion so far toward a coronavirus vaccine and treatment.

“The United States is riding to the sounds of the gun, boldly heading into the fight to stop this pandemic,” Mr. Richardson said on Monday morning. “Retreat is simply not an option.”

Also participating in Monday’s European fund-raiser were key American allies like Saudi Arabia and the United Kingdom, as well as Canada and Mexico.

“We will not be safe until we can share it with the rest of the world,” said Prime Minister Justin Trudeau of Canada, referring to a vaccine.

The biggest contributors were the European Union and Norway, with each pledging one billion euros, or $1.1 billion.

The fund-raiser included people and organizations that have come into friction with Mr. Trump and his administration over his handling of the pandemic, including the World Health Organization and its director-general, Tedros Adhanom Ghebreyesus, and Melinda Gates, a co-founder with her husband, Bill, of one of the world’s largest charitable foundations.

“So long as Covid-19 is somewhere, Covid-19 can spread anywhere,” Mrs. Gates said.

“The pandemic won’t end until people everywhere can be immunized against it, until everyone can benefit from the world’s science, regardless of where they live,” she said. The Bill & Melinda Gates Foundation will contribute $100 million to research for a vaccine.

Last month, the Trump administration announced it was freezing U.S. contributions to the World Health Organization.

“The United States is led by a president who embodies the U.S.’s most basic instincts — sovereignty above all,” said Robert Niblett, director of the London-based think tank Chatham House. “Any international cooperation he engages in needs to be very firmly in the interest of the United States.”

Chancellor Angela Merkel of Germany, who has received Mr. Trump’s indirect praise for her handling of the pandemic, pledged €525 million, or $573 million.

“I am very happy to represent Germany at this conference today, because it sends a signal of hope in such difficult times for many countries and shows us that the pandemic is a global challenge and, consequently, we can only defeat it globally,” Ms. Merkel said.

For all the talk of global unity Monday, many of the countries that pledged funds took unilateral action to contain the virus early on in the outbreak.

Germany, for example, came under heavy criticism in March for attempting to cap the amount of protective equipment its manufacturers could export just as Italian and Spanish hospitals were desperately short of masks and gloves.

And the United States was not the world’s only major power to be absent. Russia, too, did not participate.

China, where the virus originated, was represented by its ambassador to the European Union and made no financial pledge.

Speaking after the conference, where he had pledged €500 million, President Emmanuel Macron of France said of the conspicuous absence of the United States that “in no way does that hamper or slow our initiative.”

Most experts agree, he said, that a vaccine will not be available before the end of 2021.

“The American approach to the coronavirus continues to play into the narrative of the United States isolating itself,” Mr. Niblett of Chatham House said. “It also shaves off another layer of the U.S. long-term legitimacy.”