New Delhi: Adar Poonawalla's Serum Institute of India (SII), the maker of coronavirus vaccine Covishield in India, has reportedly been served a legal notice by AstraZeneca over vaccine supply delays.

Adar Poonawalla, the Chief Executive Officer of Serum Institute of India on Tuesday said that pharmaceutical company AstraZeneca has sent Serum Institute a legal notice over delays in supplying the vaccine.

The news emerged a day after Mr Poonawalla admitted in an interview to NDTV that existing production capacity to manufacture Covishield, one of the two vaccines being administered in India, is "very stressed, to put it frankly".

He also said the government's pause on major Covishield shipments to other countries and the 'first claim' deal with India were difficult to explain abroad, where the vaccine was sold at a substantially higher cost per dose.

"The globe needs this vaccine and we are prioritising the needs of India at the moment and we are still short of being able to supply... to every Indian that needs it," Poonawalla said.

However, last week the centre said there was no outright ban on the export of vaccines.

Meanwhile, the world's largest vaccine maker has appealed to the Indian government for financial help after New Delhi restricted exports of its coronavirus jabs to battle a surge in cases at home.

Poorer countries around the world, as well as some rich nations, have relied heavily on the Serum Institute of India (SII) for supplies of the AstraZeneca vaccine but last month the government put the brakes on allowing it to export the shots.