The US is to send 1.5 million doses of the AstraZeneca vaccine to Canada.
In a similar loan deal, they are to send 2.5 million doses to Mexico, an administration official told Reuters today.
The US is to send both countries the shipments of the vaccine soon with the understanding that they will return a similar shipment amount back in the future.
The AstraZeneca vaccine has been authorized for use in other countries but has yet to be cleared by the Federal Drug Administration (FDA).
Two officials told Reuters that the vaccine would be delivered to both Canada and Mexico in "short order" once the deal was completed, but they declined to give a more specific timetable.
AstraZeneca has manufactured millions of doses in the US and said that it would have 30 million shots ready at the beginning of April.
News of the announcement comes less than 24 hours since Taoiseach Micheál Martin and US President Joe Biden had a virtual meeting to mark St Patrick's Day.
Mr Martin had played down any expectations that he would request coronavirus vaccine doses from US President Joe Biden during his first bilateral meeting.
Speaking on US TV’s ‘Face the Nation’ on Sunday, Mr Martin noted that he wasn’t aware of “too many countries that are giving their vaccines away.
We will obviously discuss covid and we’ll discuss vaccination.”
Asked about reports that the EU has already requested AstraZeneca vaccines from the United States but was rebuffed, he replied:
“I am not pre-empting any discussions I will have in detail with the president but obviously the broader covid vaccination issue will of course be discussed.”