President Donald Trump signaled that he could veto any tightening of U.S. rules for the emergency clearance of a coronavirus vaccine, a move that could increase concerns that the race to find a COVID-19 shot is being politicized ahead of the presidential election.

The Food and Drug Administration is expected to soon issue final guidelines for an emergency-use authorization for a vaccine. Regulators and drugmakers have in recent weeks vowed to adhere to science, not politics, in deciding when a vaccine is ready to reach the market.

At a news conference on Wednesday, Trump said it “sounds like a political move” when asked whether the FDA was considering stricter standards for an authorization, suggesting that the White House could intercede if it thought the agency was too rigorous.

“That has to be approved by the White House,” Trump said. “We may or may not approve it.”

Representatives for the FDA didn’t immediately respond to calls and emails requesting comment.

Companies including Pfizer Inc., Moderna Inc., AstraZeneca Plc and Johnson & Johnson have vaccine candidates in late-stage clinical trials. Some of those studies could produce data on efficacy as soon as October.

Trump is trailing Democrat Joe Biden in polls ahead of the November election, with surveys showing that a majority of Americans disapprove of the president’s handling of the virus. Trump has sought to focus on other topics while claiming that his administration is doing a good job handling the virus.

The president has been promising that a coronavirus vaccine will be approved within weeks -- a gambit to turn a pandemic cure into an October surprise for his struggling re-election campaign.

Trump and his supporters have also questioned whether government employees are trying to sabotage his efforts to combat the virus. In August, the president attacked the FDA for harboring “deep state” staff slowing vaccine and drug work to hurt him politically. There’s no evidence that’s the case.