WASHINGTON (AP) — After expressing frustration at the slow pace of approval for coronavirus treatments, President Donald Trump was set to announce on Sunday the emergency authorization of convalescent plasma for COVID-19 patients.

The announcement will come after days of White House officials suggesting there were politically motivated delays by the Food and Drug Administration in approving vaccine and therapeutics for the disease that has upended Trump's reelection chances.

On the eve of the Republican National Convention, Trump was set to issue the emergency order — which would make it easie...