Drug company AstraZeneca is to start producing a potential vaccine for coronavirus, its boss has told the BBC.

Trials of the drug are under way but Pascal Soriot said the firm must start making doses now so that it can meet demand if the vaccine proves effective.

"We are starting to manufacture this vaccine right now - and we have to have it ready to be used by the time we have the results," he said.

AstraZeneca says it will be able supply two billion doses of the vaccine.

Speaking to the BBC's Today programme, Mr Soriot said manufacturing was beginning already because, "we want to be as fast as possible".

"Of course, with this decision comes a risk but it's a financial risk and that financial risk is the vaccine doesn't work," he added.

"Then all the materials, all the vaccines, we've manufactured will be wasted."

He said AstraZeneca would not seek to make a profit from producing the drug during the pandemic.

If it works, the company will be able to produce two billion doses after signing two new contracts on Thursday, one of which was with billionaire philanthropist Bill Gates.

AstraZeneca, which is developing the vaccine with scientists at Oxford University, has agreed to supply half of the doses to low and middle-income countries.

One of the new partnerships is with the Serum Institute of India (SII), the world's largest manufacturer of vaccines by volume. The other is a $750m (£595m) deal with two health organisations backed by Bill and Melinda Gates.