GENEVA (AP) — The U.N.-backed program to ship COVID-19 vaccines worldwide has announced supply delays for up to 90 million doses from an Indian manufacturer, in a major setback for the ambitious rollout aimed to help low- and middle-income countries fight the pandemic.

Gavi, the Vaccine Alliance, said Thursday that the delays come as India is facing a surge of coronavirus infections that will increase domestic demands on the Serum Institute of India, a pivotal vaccine maker behind the COVAX program.

The move will affect up to 40 million doses of the Oxford University-AstraZeneca vaccines being manufactured by the Serum Institute that were to be delivered for COVAX this month, as well as 50 million expected next month. Gavi said it has notified recipient countries.

The institute has been contracted to supply vaccines to 64 countries, and Gavi said the U.N.-backed program has “notified all affected economies of potential delays.”

Gavi, which runs COVAX jointly with the World Health Organization and the Coalition for Epidemic Preparedness Innovations, has already distributed 31 million doses of the AstraZeneca vaccine -- 28 million from the Serum Institute and another 3 million from a South Korean contractor also producing the vaccine.