WASHINGTON: The United States will release up to 60 million doses of the AstraZeneca Covid-19 vaccine, a senior official said Monday, following mounting criticism that the Biden administration was hoarding shots while other countries suffered.

“US to release 60 million Astra Zeneca doses to other countries as they become available,” tweeted Andy Slavitt, senior advisor to the White House on Covid 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.”

White House spokeswoman Jen Psaki told reporters the Food and Drug

The move greatly expands an action from last month to loan four million doses of the AstraZeneca vaccine, which is not yet approved in the United States and may never be, to Mexico and Canada.

Almost 140 million people in the US have now received one dose — 42 percent of the population — or 53 percent of the adult population.

The rate of new Covid cases is once more declining and a month-long mini spike now appears over.

Pfizer and Moderna appear on track to deliver 600 million doses between them by the end of July. The United States has also resumed vaccinations with the Johnson & Johnson shot, the third authorized injection, after a brief pause over links to a rare form of clotting.