WASHINGTON (AP) — The U.S. Postal Service has sent letters to 46 states — including Missouri — warning it cannot guarantee all ballots cast by mail for the November election will arrive in time to be counted.

That’s according to a report published Friday by The Washington Post.

Postal Service official Thomas Marshall told Missouri Secretary of State Jay Ashcroft last month that the service might not be able to return all mail-in ballots to election officials by Nov. 3.

Missouri requires mail ballots to arrive by Election Day for them to be counted.

Marshall says Missouri should encourage voters to mail ballots no later than Oct. 27.

The revelation that many voters could be disenfranchised if they try to vote by mail comes amid a campaign by President Donald Trump to sow doubts about the election.

Though Trump casts his own ballot by mail, he’s railed against efforts to allow more people to do so, which he argues without evidence will lead to increased voter fraud.

The Postal Service is bracing for an unprecedented number of mail-in ballots as a result of the coronavirus pandemic.