World leaders called Monday for cooperation not competition in the quest for a coronavirus vaccine, as they pledged 7.4 billion euros ($8.1 billion) at a fundraising telethon snubbed by the United States.

COVID-19 has killed nearly a quarter of a million people around the world -- 140,000 of them in Europe -- and Ursula von der Leyen, head of the European Commission and the host of the videoconference, said a vaccine is the best chance of beating the disease.

World Health Organization chief Tedros Adhanom Ghebreyesus hailed the fundraising as a powerful show of "global solidarity".

Major European powers, along with Japan and Canada, made the biggest pledges from around 40 countries, but there was no official US representation, weakening the event and raising the prospect of an uncoordinated competition to develop and produce a vaccine.

Some wealthy American individuals did take part, and pop star Madonna's million-dollar contribution was feted by EU officials.

'A down payment'

The conference narrowly missed its target of 7.5 billion euros -- although a handful of contributors did not put a sum on their pledges -- but UN chief Antonio Guterres warned much more would be needed, putting the final sum required near 38 billion euros.

"These funds are a kind of down payment for the development of new tools at the speed needed," Guterres told the conference. "But to reach everyone everywhere we likely need five times that amount."

In total around 40 countries, along with UN and philanthropic bodies -- including the Bill and Melinda Gates Foundation -- and research institutes made donations.

But the initiative was undermined by the absence of the United States, with President Donald Trump in open warfare with the WHO over its handling of the pandemic.

Trump -- fighting for reelection in November -- said Sunday that the United States will have a coronavirus vaccine ready by the end of the year.

His prediction was met with scepticism in some quarters, with Germany's Health Minister Jens Spahn warning it could take years for anyone to develop a vaccine.

US 'isolating themselves'

While putting an upbeat gloss on the event in public, privately EU officials were disappointed the US did not take part.

"The EU responded favourably to a call for global action, the US refused. They are the ones who are isolating themselves," one official said.

"We're only at the start of the process. We hope the American government will join the common effort."

A spokesperson for the US mission to the United Nations in Geneva said Washington "welcomes efforts by other countries to mobilise resources to mitigate and ultimately end the COVID-19 pandemic."

But other leaders are concerned that Trump's "America First" approach will lead to a counterproductive trans-Atlantic race to find a vaccine, and called instead for a collaborative approach.

British Prime Minister Boris Johnson told the conference that the world "must work together to build an impregnable shield around all our people".

"The race to discover the vaccine to defeat this virus is not a competition between countries, but the most urgent shared endeavour of our lifetimes."

Johnson's Japanese counterpart Shinzo Abe echoed his call, urging the international community to "unite to overcome the crisis".

French President Emmanuel Macron said it was vital that once developed, the vaccine be treated as "global public property" with access available for "the whole of the planet".

'Vaccine war'

Isabelle Marchais, an expert with the Delors Institute thinktank, said the US was ready to "put all its forces into the battle" to win a "vaccine war".

In March, Germany was forced to insist that the rights to coronavirus vaccine research were not for sale after reports Trump wanted the US to buy exclusive access to one being developed by a German biotech firm.

In recent days the Trump administration has stepped up pressure on China, where the outbreak began, claiming it originated in a laboratory in the city of Wuhan.

Without mentioning Washington, China implicitly hit back at the donor conference, where it was represented by its ambassador to the EU.

"Multilateral cooperation in fighting the virus, confidence and solidarity are much more valuable than gold," ambassador Zhang Ming said. "Panic and blame game are not useful at all."

In an analysis published Monday, Marchais said more than 100 vaccine research projects were under way around the world, including eight at the stage of clinical trials in the US, China and Europe.

"Given the stakes in the current pandemic, some companies -- particularly American and Chinese ones -- are ready to start production before the end of clinical trials in order to be the first ones to get the vaccine to market," she wrote.

Of the 7.5 billion euros, four billion will go on vaccine development, two billion on the search for a treatment and 1.5 billion for producing tests, the EU said.