France on Thursday (May 14) said equal access to any coronavirus vaccine developed by Sanofi was non-negotiable.
It added that no country such as the United States should have priority for financial reasons.
The French government's robust comments came a day after the chief executive of the French pharmaceutical giant, Paul Hudson, said vaccine doses produced in America could go to U.S. patients first.
As the French backlash strengthened, Sanofi clarified that it would be made available to all.
Hudson's comments have reportedly upset President Emmanuel Macron, whose office said a presidency official would meet with Sanofi representatives next week.
On Thursday, French Prime Minister Edouard Philippe said on Twitter:
"A vaccine against COVID-19 should be a public good for the world. The equal access for all to the vaccine is non-negotiable"
Sanofi is currently working on two vaccine projects against COVID-19.
One is with British rival GlaxoSmithKline, which has received financial support from the U.S. Health Department.
It's working on another project with U.S. company Translate Bio that will use a different technology.
The controversy has raised questions over whether Europe has been too slow to respond in terms of organising and funding vaccine research.
Sanofi has called for stronger European coordination in the hunt for a vaccine.