House and Senate lawmakers want U.S. Food and Drug Administration Commissioner Stephen Hahn to testify about whether his agency is being politically pressured to quickly approve a COVID-19 vaccine and other products before they have demonstrated safety and efficacy.

Senate Democrats also want U.S. Centers for Disease Control and Prevention Director Robert Redfield to come to Capitol Hill.

A number of lawmakers and scientific and public health experts have raised concerns about the FDA's independence after President Donald Trump and other members of his administration publicly criticized the agency and said they expected regulators to approve a vaccine before the end of the year — even as early as the Nov. 3 election.

Trump also openly pressured the FDA to grant emergency use authorization, or EUA, to hydroxychloroquine — an action that was later revoked — and convalescent plasma.

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Hahn told the Financial Times Aug. 30 he was willing to grant an EUA to COVID-19 vaccines before late-stage human trials are completed — remarks that stirred more concern within the scientific and public health communities about whether the FDA was being pressured to rush its decisions for political reasons.

The FDA chief told CBS News Aug. 31 that a decision for an EUA on a COVID-19 vaccine could come by election day. It is highly unusual for regulators to make public predictions about when products may enter the U.S. market.

Hahn would not say whether he would resign if he was pressured by Trump to rush a vaccine to the market.

"There's been pressure throughout this pandemic," Hahn told CBS. "I think anybody who doesn't acknowledge that would be kidding themselves."

Democratic leaders of the House Energy and Commerce Committee said they were even more concerned about the FDA's independence after bipartisan members of the panel held an Aug. 31 teleconference with Hahn to discuss matters related to experimental products to treat and prevent COVID-19, which has killed about 184,000 Americans.

They called for Hahn to appear before the committee at a yet-to-be scheduled hearing sometime in September. Reps. Frank Pallone, D-N.J., chairman of the committee, Anna Eshoo, D-Calif., chairwoman of the health subcommittee, said the decision to hold the hearing was made on a bipartisan basis.

"The American people must be able to trust FDA," Pallone and Eshoo said in an Aug. 31 statement. But recent events, including Hahn's misleading claims about the efficacy of convalescent plasma, "raise serious concerns that the Trump administration is increasing political pressure on the agency and interfering with its regulatory independence," they said.

From the White House podium on Aug. 23, Hahn had wrongly claimed data showed convalescent plasma provided a "35% improvement in survival," which he called "a pretty substantial clinical benefit." He said that meant that out of 100 people sick with COVID-19, "35 would have been saved because of the admission of plasma" — a claim that was false and misleading.

Health and Human Services Secretary Alex Azar made similar misleading remarks.

Hahn later blamed the misleading information on his confusion over absolute risk reduction with relative risk reduction. He was widely criticized by the scientific and public health communities for getting the information wrong.

Pallone and Eshoo said they pressed Hahn and the two other FDA officials — Center for Biologics Evaluation and Research Director Peter Marks and acting Center for Drug Evaluation and Research Director Patrizia Cavazzoni — about the agency's Aug. 23 decision to grant an EUA to convalescent plasma as a treatment for COVID-19.

Plasma is the liquid part of blood. People who recover from infectious diseases, like COVID-19, may have antibodies in their blood capable of fighting the virus. The product was already available to COVID-19 patients under an FDA-monitored, U.S. taxpayer-funded expanded access program run by the Mayo Clinic before the EUA was granted.

The lawmakers also questioned Hahn and the FDA officials about what led to HHS deciding to let laboratory-developed tests for COVID-19 onto the U.S. market without any regulatory review.

Senators press for hearing

Meanwhile, Democratic members of the Senate Health, Education, Labor and Pensions Committee asked the panel's bipartisan leaders, Sens. Lamar Alexander, R-Tenn., and Patty Murray, D-Wash., to call Hahn and Redfield to testify.

Along with questions about whether the FDA is being pressured to approve vaccines and therapeutics, the lawmakers want to ask Redfield about what was behind the Trump administration's revisions to the CDC's testing recommendations — a decision that created confusion for the medical community.

U.S. National Institute of Allergy and Infectious Diseases Director Anthony Fauci was having surgery and was not part of the White House Coronavirus Task Force's Aug. 20 decision to urge against testing people who have no symptoms of COVID-19, even if an individual thinks they may have been exposed to the virus.

After much criticism, Redfield issued a late-night statement Aug. 26 saying "testing may be considered for all close contacts of confirmed or probable COVID-19 patients," which created more confusion.

It is unclear whether the White House will permit or try to block Hahn and Redfield from testifying before the House and Senate.