The heads of Canada and Mexico on Thursday will pledge to share millions of vaccine doses with other countries in need at the first gathering of North American leaders at the White House since 2016.

Canadian Prime Minister Justin Trudeau and Mexican President Andrés Manuel López Obrador will meet with President Biden for the North American Leaders Summit, where the three will discuss economic initiatives, migration, climate change and the pandemic.

The leaders will announce that Canada and Mexico will send millions of vaccines to other nations in the region as part of an agreement to pay forward doses after the U.S. first shared millions of the shots with its neighbors, a senior Biden administration official told reporters on a call previewing the summit.

The exact number of doses, recipients and timing of the donations will be determined by health experts and announced at a later date, the official said, but it will be part of a broader effort to expand vaccine production capabilities in the region.

“We’re going to have public health experts determine the timing and the amount and the types of doses so that we’re working — North America — not just for our own well-being and competitiveness, but as a way to project in supporting our regional partners to come back from the pandemic stronger than before,” a senior administration official said.