BRUSSELS (AP) — World leaders on Monday pledged billions of euros for research to find a vaccine against the new coronavirus, but warned that it is just the start of an effort that must be sustained over time to beat the disease.

At a video-conference summit, U.N. Secretary General Antonio Guterres said that the 7.5 billion euros ($8.2 billion) target being sought to help find a vaccine, new treatments and better tests for the disease would be merely a "down-payment" on the tools that will be needed to fight the virus.

"To reach everyone, everywhere, we likely need five times that amount," Guterres said.

Two hours into the EU-hosted summit, just over 5.4 billion euros had been pledged, according to a European Commission tally.

Governments have reported around 3.5 million infections and more than 247,000 deaths from the virus, according to a count by Johns Hopkins University. But deliberately concealed outbreaks, low testing rates and the strain on health care systems mean the true scale of the pandemic is much greater.

People in many countries across the globe, and notably in Europe this week, are cautiously returning to work but authorities remain wary of a second wave of infections, and a vaccine is the only real golden bullet to allow something like normal life to resume.

"The reality is that we will have to learn to live with the virus until and unless we develop a vaccine," said European Commission President Ursula von der Leyen, as she announced a pledge of 1 billion euros from the EU's executive arm.

"More will be needed. So today is only the start of a global pledging marathon," von der Leyen said.

President Emmanuel Macron also warned that "a race against time is underway," as he donated 500 million euros on behalf of France.

Apart from many European leaders, heads of state and government from Australia, Canada, Israel, Japan, Jordan, South Africa and Turkey were also due to speak, along with China's EU ambassador. The United States, where more than 67,000 people have died, was a notable absentee, as was Russia.

The video-conference's aim is to gather around 4 billion euros ($4.37 billion) for vaccine research, some 2 billion euros for treatments and 1.5 billion ($1.64 billion) for testing.

British Prime Minister Boris Johnson said that "the race to discover the vaccine to defeat this virus is not a competition between countries, but the most urgent shared endeavor of our lifetimes."

Among the larger contributions, Japan pledged more than $800 million while Germany offered 525 million euros. Italy and Spain, perhaps the hardest hit by the virus in Europe, each said they would provide more than 100 million euros. The Netherlands and Israel also pledged 192 million euros and 60 million dollars respectively.

About 100 research groups are pursuing vaccines, with nearly a dozen in early stages of human trials or poised to start. But so far there's no way to predict which — if any — vaccine will work safely, or even to name a front-runner.

Dr. Anthony Fauci, the U.S. government's top expert, has cautioned that even if everything goes perfectly, developing a vaccine in 12 to 18 months would set a record for speed.

Even if a first useful vaccine is identified, there won't be enough for everyone initially. A growing number of vaccine makers say they're already starting to brew tons of doses — wasting millions of dollars if they bet on the wrong candidate but shaving a few months off mass vaccinations if their choice pans out.

EU officials say that pledges made toward vaccine research since Jan. 30, not just on Monday, will also be counted as donations toward the 7.5 billion euro target of the conference.

On a conference call with reporters, two senior U.S. officials sidestepped questions about the Trump administration's decision not to take part.

The officials, who weren't authorized to discuss the matter by name and spoke on condition of anonymity, suggested that U.S. participation was not necessary because the United States remains the world's largest donor to global health initiatives, even after the suspension of funding to the WHO.

They said that many of the programs being discussed at the conference were already funded by the U.S.

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Sylvie Corbet in Paris, and Matthew Lee in Washington, contributed to this report.

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