BEIJING (REUTERS) - China's CanSino Biologics (CanSinoBIO) has proposed supplying "tens of million of doses" of its single-dose Covid-19 vaccine to global vaccine-sharing scheme Covax, a senior company executive said.

China has four locally developed Covid-19 vaccines approved for public use and pledged earlier to supply 10 million doses to Covax without specifying the time frame of delivery.

CanSinoBIO, Sinovac Biotech and China National Pharmaceutical Group (Sinopharm) have applied to join the initiative.

Mr Pierre Morgon, senior vice-president at CanSinoBIO, said the firm made the proposal in December to supply vaccines between late 2021 and the end of 2022.

"We are happy to go beyond 2022 if there was still an expectation to do so," he told Reuters in an interview, adding it made its offer at a middle single-digit US dollar per dose.

"I can't tell you the exact number, but I can tell you, it's a very competitive price," Mr Morgon said.

The offering to Covax, which is backed by the World Health Organisation (WHO), is the lowest price in the "tiered pricing mechanism" that CanSinoBIO uses in markets outside China, where richer countries are subject to higher prices.

There is a more than threefold factor difference between the highest price offer and the lowest, Mr Morgon said.

Its vaccine, jointly developed with China's military research institute, is approved for use in China, Pakistan, Hungary and Mexico.

The three Chinese vaccine-makers are still awaiting decisions on whether they can be included in the WHO's Emergency Use Listing, a prerequisite to join Covax.