President Donald Trump speaks to the 2020 Council for National Policy Meeting, Friday, Aug. 21, 2020, in Arlington, Va. (AP Photo/Evan Vucci)

WASHINGTON (AP) — President Donald Trump announced Sunday the emergency authorization of convalescent plasma for COVID-19 patients, in a move he called “a breakthrough,” one of his top health officials called “promising,” and other health experts said needs more study before it’s celebrated.

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

On the eve of the Republican National Convention, Trump put himself at the center of the FDA’s announcement of the authorization — it makes it easier for some patients to obtain the treatment — in a news conference Sunday evening.

The blood plasma, taken from patients who have recovered from the coronavirus and rich in antibodies, may provide benefits to those battling with the disease. But the evidence so far has not been conclusive about whether it works, when to administer it and what dose is needed.

In a letter describing the emergency authorization, the chief scientist for the FDA, Denise Hinton, noted: “COVID-19 convalescent plasma should not be considered a new standard of care for the treatment of patients with COVID-19. Additional data will be forthcoming from other analyses and ongoing, well-controlled clinical trials in the coming months.”

An emergency use authorization is not the same as full FDA approval.

In the authorization letter, FDA officials emphasized convalescent plasma is still under investigation. “COVID-19 convalescent plasma should not be considered a new standard of care for the treatment of patients with COVID-19. Additional data will be forthcoming from other analyses and ongoing, well-controlled clinical trials in the coming months,” it said.

But Trump had made clear to aides that he was eager for a piece of good news on the battle of the pandemic, and the timing allowed him to head into the convention with momentum. He and aides billed it as a “major” development and utilized the White House briefing room to make the announcement.

Trump also displayed some rare discipline in the evening news conference, sticking to his talking points, deferring to the head of the FDA, Stephen Hahn, and only taking three questions from reporters.

The White House had grown agitated with the pace of the plasma approval, but the accusations of a slowdown, which were presented without evidence, were just the latest assault from Trump’s team on the “deep state” bureaucracy. White House chief of staff Mark Meadows did not deal in specifics, but said that “we’ve looked at a number of people that are not being as diligent as they should be in terms of getting to the bottom of it.”

“This president is about cutting red tape,” Meadows said in an interview Sunday on “This Week” on ABC. “He had to make sure that they felt the heat. If they don’t see the light, they need to feel the heat because the American people are suffering.”

The push on Sunday came a day after Trump tweeted sharp criticism on the process to treat the virus, which has killed more than 175,000 Americans and imperiled his reelection chances. The White House has sunk vast resources into an expedited process to develop a vaccine, and Trump aides have been banking on it being an “October surprise” that could help the president make up ground in the polls.