President Joe Biden on Wednesday said the US wanted to share coronavirus vaccines with other countries but would not start sending them abroad until it had enough at home.
“We’re looking at what is going to be done with some of the vaccines that we are not using," Mr Biden said.
"We’ve got to make sure they are safe to be sent. And we hope to be able to be of some help and value to countries around the world.”
He spoke at an event marking the 200-millionth administered vaccine of his presidency and a "new phase" in which he urged American adults to be vaccinated as soon as possible.
The administration has so far "lent" 4.2 million doses of the AstraZeneca vaccine, which is not yet authorised for use in the US, to Canada and Mexico.
Mr Biden said he spoke on Wednesday to Canadian Prime Minister Justin Trudeau and indicated that another loan might be coming, but there could be delays.
“We helped a little bit there. We’re going to try and help some more,” he said.
“But there’s other countries as well that I’m confident we can help, including in Central America. So, it’s in process.
"We don’t have enough to be confident to send it abroad now but I expect we’re going to be able to do that.”
Biden thanks healthcare workers and volunteers as US hits 200 million vaccinations
It is not clear whether Mr Biden would consider sharing more AstraZeneca doses before the US has enough vaccine.
