The Donald Trump administration has urged U.S. states to get ready to distribute a potential COVID-19 vaccine by Nov. 1, in the latest sign of the accelerating race to deliver a vaccine by year's end.

"CDC urgently requests your assistance in expediting applications for these distribution facilities," read an Aug. 27 letter from Robert Redfield, director of the Centers for Disease Control and Prevention (CDC).

Dallas-based wholesaler McKesson Corp. has a deal with the federal government to set up centers to distribute a coronavirus vaccine when it becomes available.

The CDC, "if necessary, asks that you consider waiving requirements that would prevent these facilities from becoming fully operational by Nov. 1, 2020," two days before the U.S. presidential election, said the letter.

The U.S. Food and Drug Administration (FDA) has raised the possibility that a vaccine might be given emergency approval before the end of trials designed to ensure its safety and effectiveness.

A request for such extraordinary approval would have to come from the vaccine developer, FDA chief Stephen Hahn told the Financial Times in an interview published Sunday.

The CDC provided states with documents giving details of a vaccine rollout plan, adding that vaccines would either be approved as licensed vaccines or under emergency use authorization.

Recipients would probably require a second "booster" dose, according to the documents.

"Vaccine and ancillary supplies will be procured and distributed by the federal government at no cost to enrolled COVID-19 vaccination providers," the documents say.