Drugs giant AstraZeneca has announced it is ready to provide a potential new coronavirus vaccine from September.
The firm said it had concluded deals to deliver at least 400 million doses of the vaccine, which it is developing with Oxford University.
AstraZeneca said it was capable of producing one billion doses of the AZD1222 vaccine this year and next.
Initial trials are under way and AstraZeneca said it recognised that the vaccine might not work.
But the company said it was committed to advancing the clinical programme.
Scientists have warned that a coronavirus vaccine, if developed, might not confer full immunity, while Prime Minister Boris Johnson has warned that a vaccine might never be found.
Despite these reservations, intensive research continues, with about 80 groups around the world working on possible vaccines.
AstraZeneca indicated that production would take place in more than one country. It thanked the UK and US governments for "substantial support to accelerate the development and production of the vaccine".
It also said it was in discussions with the Serum Institute of India and other potential partners to increase production and distribution.
Specifically, it said it had received support of more than $1bn from the US Biomedical Advanced Research and Development Authority (BARDA) for the development, production and delivery of the vaccine,
AstraZeneca chief executive Pascal Soriot described the coronavirus pandemic as "a global tragedy" and "a challenge for all of humanity".
"We need to defeat the virus together or it will continue to inflict huge personal suffering and leave long-lasting economic and social scars in every country around the world," he said.
"We are so proud to be collaborating with Oxford University to turn their ground-breaking work into a medicine that can be produced on a global scale."