A senior administration official said later on Monday that there could be up to 60 million doses of the AstraZeneca vaccine available to be shared with other countries in the next two months, assuming the FDA issues an emergency use authorization for the vaccine.

"We expect that there are approximately 10 million doses that could be released, if and when FDA gets gives its concurrence, which could happen in the coming weeks. Further, there's an estimated additional 50 million doses that are in various stages of production and these could be completed in stages across May and June," the senior administration official said.

Biden and Indian Prime Minister Narendra Modi spoke on Monday. Modi did not make a specific request for vaccines when he spoke with Biden, according to senior administration officials.

One official said that the US is looking at ways it can bolster vaccine production in India and other countries, focusing specifically on mRNA vaccines. And Psaki stated on Monday that as "requested by India," the US would provide "raw materials for the production of AstraZeneca Covishield vaccine," but she did not answer if actual doses of that vaccine would go to the country.

It could be some time before other countries receive these vaccines, the White House cautioned Monday.

"Just to be clear, right now, we have zero doses available of AstraZeneca," Psaki told reporters. Following a FDA quality review, there could be 10 million available in the coming weeks, but it will likely be May or June before closer to 60 million are finished. "So, this is not immediate."

Countries have been eagerly petitioning the US for shipments of vaccines as doses are snapped up by wealthier nations. Biden administration officials have described near-daily phone calls from allies -- poor and rich alike -- seeking help securing vaccine doses.

A spokesperson for AstraZeneca said the company could not comment on specific details of the distribution plan, but underscored that the doses "are part of AstraZeneca's supply commitments to the US government."

"Decisions to send US supply to other countries are made by the US government," the spokesperson added.

The US is expected to have a surplus of vaccines in the hundreds of millions of doses. Some of those doses have already been sent to Mexico and Canada as part of what the US has referred to as a "loan." Psaki would not say on Monday whether the US would distribute its additional trove of AstraZeneca vaccines to the international community on a loan or gifted basis.

The US has taken initial steps to help other countries ramp up vaccinations, including by boosting global manufacturing and appointing Gayle Smith, a former director of the US Agency for International Development, to coordinate the international response to the coronavirus pandemic.

Political concerns have also weighed on officials, who are wary of sending doses abroad before every American can access them.

So far, nearly 54% of adults in the US have received at least one dose of Covid-19 vaccine, according to data published Monday by the US Centers for Disease Control and Prevention.

Biden said in March that if there was a surplus of vaccines, "we're going to share it with the rest of the world." However, he has repeatedly underscored that vaccines will not be sent without taking care of the American population first.

"We're looking at what is going to be done with some of the vaccines that we are not using. We got to make sure they are safe to be sent. And we hope to be able to be of some hope and value to countries around the world," Biden said earlier this month.

Other countries like Russia and China -- regimes where the political downside of sending vaccines abroad have little bearing on leaders' decision-making -- have far outpaced the US in distributing vaccines, expanding their influence in places like Southeast Asia.

This story has been updated with additional reporting.