Psaki during a White House press briefing said the Biden administration is finalizing the "loan," with some 2.5 million doses to be sent to Mexico while 1.5 million will go to Canada.
The vaccine sharing plan is not fully finalized, Psaki said, but she noted it is the aim of the Biden administration.
"Our first priority remains vaccinating the U.S. population," Psaki said at the daily briefing, though added that "ensuring our neighbors can contain the virus is a mission-critical step, is mission critical to ending the pandemic."
The AstraZeneca vaccine has not been authorized for use in the U.S. but has been by the World Health Organization. Tens of millions of doses have been stockpiled in the U.S. should it receive emergency use authorization, sparking an international outcry that lifesaving doses were being withheld when they could be used elsewhere.
The Biden administration has said that once U.S. citizens are vaccinated, the next step is ensuring Canada and Mexico are able to manage the pandemic so the borders can reopen. That could mean more vaccines for Canada faster and a shorter wait for second doses.
The loan deal will not affect President Biden’s goal of having all adult Americans eligible for a vaccine by May 1, and will not reduce the supply of available vaccine in the U.S., Reuters reported.
Although Canada’s economy is tightly interconnected with the U.S., Washington hasn’t allowed the hundreds of millions of vaccine doses made in America to be exported until now, and Canada has had to turn to Europe and Asia.
The vaccine supply chain difficulties have forced Canada to extend the time between the first shot and the second by up to four months so that everyone can be protected faster with the primary dose. The hope is to get all adults at least one shot by the end of June.
Canadian regulators have approved the Pfizer, Moderna, AstraZeneca and Johnson & Johnson vaccines, but acquiring them has proven difficult.
Canada ranks about 20th in the number of doses administered, with about 8% of the adult population getting at least one shot. That compares with about 38% in the U.K. and 22% in the U.S.
The U.S. stockpiling of the AstraZeneca vaccine has been controversial with other allies that are also looking to halt the pandemic. The 27-nation European Union had found it difficult to approach President Biden on sharing supplies of the vaccine so the disease could be stopped overseas, which would not only help save lives but also improve global economic growth.
E.U. member states’ ambassadors talked about the problem last week.
The German government has said it contacted U.S. officials about vaccine supplies but emphasized the European Commission is responsible for procurement.
The news comes as many European member states have temporarily halted the use of the AstraZeneca vaccine in recent days to investigate cases of blood clots that occurred after vaccination. Following such reports, however, a safety committee with Europe’s regulator on Thursday concluded that the vaccine safe and effective, with no ties to an overall increased risk of blood clots in vaccinated individuals. However, a definitive link to serious blood disorders could not be ruled out, the regulator said.
Still, top officials with the European Medicines Agency said the benefits of the vaccine against COVID-19 and its associated hospitalizations and deaths continue to exceed the risks of side effects.
The EMA said the safety committee will continue to run investigations to assess reports. The agency stressed awareness of the risks for both patients and providers and advised including the risks in the vaccine's product information.
Fox News’ Kayla Rivas and Kristina Biddle and the Associated Press contributed to this report.