GlaxoSmithKline Plc and Sanofi, partners developing a potential coronavirus vaccine, are discussing a 500 million pound ($620 million) deal to supply the U.K. government with the shot, assuming it’s successful, said a person familiar with the matter.

The companies plan to supply Britain with 60 million doses of the vaccine, which is under development, according to the person, who asked not to be identified because the details are still being finalized. The pending accord was first reported by the Sunday Times.

Sanofi and Glaxo are among dozens of companies and institutions sprinting to deliver a vaccine to help end the pandemic, while governments around the world seek to secure doses in advance. The partners are following a number of others like the University of Oxford, working with AstraZeneca Plc, Moderna Inc. and China’s CanSino Biologics Inc. that have started testing their shots in humans over the past few months.

Glaxo declined to comment, while Sanofi said discussions with various countries including the U.K. were ongoing. The U.K. government said in an email that it’s engaging with a wide range of companies to negotiate access to vaccines, and that announcements would be made when agreements are completed.

Sanofi, based in Paris, and Glaxo, the British pharma giant, plan to start a study compressing the early and middle stages of clinical tests in September. Sanofi said in June that it’s targeting approval in the first half of 2021, earlier than it previously expected.