COVID-19 Informer: World leaders pledge billions for coronavirus vaccine

UN Secretary General Antonio Guterres said that the 7.5 billion euro ($A12.8 billion) target would be merely a "down payment" on the tools needed to fight the virus.

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

Just over an hour into the summit, about 5 billion euros ($A8.5b) had been pledged, according to a European Commission tally.

The European Commission ($A1.7b), France ($A854m), and Germany ($A896m) kicked the can in a big way.

About 100 research groups are pursuing vaccines, with nearly a dozen in early stages of human trials or poised to start soon.

And US President Donald Trump is "very confident" of a vaccine being developed by the end of 2020.

Trump said American and Australian scientists were working together on a vaccine.

"I just want to get a vaccine that works," he told a televised Fox News virtual town hall meeting on Sunday.

"I really don't care if it's another country. I'll take my hat off to them.

"We have to come up with a vaccine. We're working with other countries. We're working with Australia, we're working with the UK."

Meanwhile the US government's leading man, Dr Anthony Fauci, has cautioned that even if everything goes perfectly, developing a vaccine in 12 to 18 months would set a record for speed.

Elsewhere, the UK is considering a number of measures for "life after lockdown" - everything from staggering arrival and departure times to reviewing office layouts and erecting security screens; Germans and Greeks have been allowed to get a haircut for the first time in more than six weeks; and Japan extended its national state of emergency to May 31.

In another development, cruise giant Carnival Corporation said on Monday that it planned to reopen cruising on eight of its ships before the end of the US summer.

Carnival has canceled service on some of its cruise lines through September, but it said it was planning to offer cruises from a number of US ports.

All Carnival Splendor cruises in Australia from June 19 to August 31 will be cancelled, the corporation said.

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