WASHINGTON, April 26 (AFP) - The United States will release up to 60 million doses of the AstraZeneca COVID-19 vaccine, a senior official said on Monday (Apr 26), following mounting criticism that the Biden administration was hoarding shots while other countries suffered.

"US to release 60 million AstraZeneca doses to other countries as they become available," tweeted Andy Slavitt, senior adviser to the White House on COVID-19 response.

It was not immediately clear how many doses are ready to be shipped or where they will go, with Slavitt adding "at this time there are still very few available".

But President Joe Biden held a telephone call with Indian Prime Minister Narendra Modi on Monday, pledging his country's "steadfast support for the people of India who have been impacted by the recent surge in COVID-19 cases".

The United States "is providing a range of emergency assistance, including oxygen-related supplies, vaccine materials and therapeutics", Biden told Modi, according to a statement.

White House spokeswoman Jen Psaki told reporters the Food and Drug Administration would perform quality checks on doses before they are sent abroad.

"Our team will share more details about our planning and who will be receiving offers from here, but we're in the planning process at this point in time," she added.

President Joe Biden's government has been under pressure to lift restrictions on exporting vaccine and vaccine supplies as countries like India experience massive surges while US supply appears increasingly assured and domestic demand begins to taper off.