LONDON — Pharma giants GlaxoSmithKline and Sanofi Pasteur have announced they will supply 100 million doses of its experimental COVID-19 vaccine to the United States as governments buy up supplies in hopes something will work.

The United States will pay up to $2.1 billion "for development including clinical trials, manufacturing, scale-up and delivery of its vaccine,'' the companies said in a statement. Sanofi will get the bulk of the funds.

 The U.S. government has a further option for the supply of an additional 500 million doses longer term as part of its Operation Warp Speed program. 

"The portfolio of vaccines being assembled for Operation Warp Speed increases the odds that we will have at least one safe, effective vaccine as soon as the end of this year," U.S. Health and Human Services Secretary Alex Azar said in a statement. "Today's investment supports the Sanofi and GSK adjuvanted product all the way through clinical trials and manufacturing, with the potential to bring hundreds of millions of safe and effective doses to the American people."

Earlier this week the British government signed a deal for 60 million doses of a potential coronavirus vaccine that could start to be rolled out in the first half of next year. 

Britain's GSK and France's Sanofi's vaccine prospect is based on the existing DNA-based technology that is used to produce Sanofi's seasonal flu vaccine. It is one of several vaccines in development.

"The global need for a vaccine to help prevent COVID-19 is massive, and no single vaccine or company will be able to meet the global demand alone," said Thomas Triomphe, executive vice president of Sanofi Pasteur. 

The companies said discussions are ongoing with the European Commission.