The French pharmaceutical giant Sanofi has rowed back on an apparent promise to prioritise the US market with any potential Covid-19 vaccine.

Sanofi CEO Paul Hudson sparked a row by saying the US government had "the right to the largest pre-order because it's invested in taking the risk".

French Prime Minister Edouard Philippe responded by saying access for all was "non-negotiable".

Sanofi's chairman has now vowed equal access for everyone.

"I am going to be extremely clear: there will be no particular advance for any country," Serge Weinberg told France 2 TV.

He said Mr Hudson's words had been distorted.

Prime Minister Philippe said he had spoken to Mr Weinberg and received "all the necessary assurance regarding the distribution of an eventual Sanofi vaccine".

President Emmanuel Macron said that recent efforts had proved a vaccine should not be subject to market forces and he is due to meet top Sanofi officials next week.

The EU insisted that all countries should get equal access to a vaccine. "The vaccine against Covid-19 should be a global public good and its access needs to be equitable and universal," said European Commission spokesman Stefan de Keersmaecker, quoted by AFP news agency.

Why is the issue so delicate for Sanofi?

The deadly coronavirus pandemic has made the search for a Covid-19 vaccine the top priority for labs worldwide, with intense pressure to speed up a process that usually take years to develop.

Earlier this month the EU chaired a global online summit to boost coronavirus research, and secured pledges of $8bn (£6.5bn) from some 40 countries and donors. The funding is aimed at developing a coronavirus vaccine and treatments for Covid-19.

The UK co-hosted the summit but the US and Russia did not take part.

Sanofi's Covid-19 vaccine research is partly funded by the US Biomedical Advanced Research and Development Authority (Barda) but in recent years Sanofi received tens of millions of euros in tax credits from the French government to help its research.

Mr Hudson's remarks in a Bloomberg interview provoked uproar among politicians on the right and left in France. The Socialists estimated that Sanofi had received some €150m (£133m; $162m) in research tax credit and millions more in other tax credit.

Sanofi's chief in France, Olivier Bogillot, said the goal was to have a vaccine "available to the US as well as France and Europe at the same time".

But speaking on French news channel BFMTV, he said this would only be possible "if Europeans work as quickly as the Americans", and added that the US government had pledged to spend "several hundreds of millions of euros".

The row was reminiscent of reports in March of a US attempt to buy German biotech firm CureVac, which has also been researching a possible vaccine. CureVac insisted there had been no US attempt to buy the firm or its manufacturing capacity.

Last month Sanofi also teamed up with Britain's GlaxoSmithKline (GSK) to work on a vaccine, though trials have not yet started.

Sanofi's head of vaccine research, John Shiver, says "we are using an existing technology that was designed for influenza, and we're applying it to the new virus that causes Covid-19 disease".

Sanofi says GSK "will contribute its adjuvant technology, an ingredient added to enhance the immune response, reduce the amount of vaccine protein required per dose and improve the chances of delivering an effective vaccine that can be manufactured at scale".

The candidate vaccine is expected to enter clinical trials in the second half of 2020 and to be available by the second half of 2021.