"It makes sense for the United States to loan its surplus of millions of doses to neighbors where it can be put to good use right away," said Joshua Busby, assistant professor of public affairs at the University of Texas-Austin.

The pending deals with Canada and Mexico, Busby told VOA, do not go far enough because "more countries in the Americas and beyond will need vaccines. But I'm confident that the Biden team is aware of this."

Busby, author of the book "Moral Movements and Foreign Policy," said he expects in the coming months the Biden administration will make a major effort to increase global vaccine access "because the longer the epidemic persists globally, the greater the risk of variants that could emerge for which the current vaccines are ineffective."

Asked on Thursday about requests from other countries to make U.S. coronavirus vaccine stock available to them, Psaki replied: "Certainly we'll have those conversations, and we are open to receiving those requests and obviously making considerations."