President Donald Trump is expected to sign an executive order on Tuesday aimed at prioritizing the shipment of the coronavirus vaccine to Americans before other nations, according to senior administration officials.

The signing is slated to take place during a vaccine summit at the White House, with the hope that the order will allay fears that there will not be enough doses of the vaccine to go around after distribution begins.

White House officials described the order as a “reaffirmation of the President’s commitment to America first.” But on a call with reporters Monday evening, in which administration officials asked not to be identified publicly, the White House did not provide specifics on how the order will do that.