WASHINGTON – President Donald Trump said on Wednesday that the White House “may or may not” approve new Food and Drug Administration guidelines that would toughen the process for approving a coronavirus vaccine, and suggested the plan “sounds like a political move.”

The pronouncement once again undercut government scientists who had spent the day trying to bolster public faith in the promised vaccine. Just hours earlier, four senior physicians leading the federal coronavirus response strongly endorsed the tighter safety procedures, which would involve getting outside expert approval before a vaccine could be declared safe and effective by the FDA.

The president’s comments, to reporters in the White House briefing room, came after the doctors told a Senate panel that they had complete faith in the FDA, and that science and data — not politics — were guiding its decisions. Last week, Trump used the same setting to declare that the director of the Centers for Disease Control and Prevention had “made a mistake” when he said most Americans would not complete the vaccination process until next summer and that masks were at least as important as a vaccine to control the virus’ spread.

The FDA had planned to issue stricter guidelines for the emergency authorization of any new coronavirus vaccine, which would add a new layer of caution to the vetting process, even as the president has insisted a vaccine will be ready as early as next month. Trump, though, cast doubt on the FDA plan.

“That has to be approved by the White House,” he said, adding, “We may or may not approve it.” Raising questions about why vaccine-makers would want to delay the process, he said, “We are looking at that, but I think that was a political move more than anything else.”

He pointedly said he had “tremendous trust in these massive companies” that are testing the vaccines, adding, “I don’t know that a government as big as” the federal government could do as well.