WASHINGTON — Top White House officials are blocking strict new federal guidelines for the emergency release of a coronavirus vaccine, objecting to a provision that would almost certainly guarantee that no vaccine could be authorized before the election on Nov. 3, according to people familiar with the approval process.

Facing a White House blockade, the Food and Drug Administration is seeking other avenues to ensure that vaccines meet the guidelines. That includes sharing the standards — perhaps as soon as this week — with an outside advisory committee of experts that is supposed to meet publicly before any vaccine is authorized for emergency use. The hope is that the committee will enforce the guidelines, regardless of the White House’s reaction.

The struggle over the guidelines is part of a monthslong tug of war between the White House and federal agencies on the front lines of the pandemic response. White House officials have repeatedly intervened to shape decisions and public announcements in ways that paint the administration’s response to the pandemic in a positive light.

That pattern has dismayed a growing number of career officials and political appointees involved in the administration’s fight against a virus that has claimed more than 209,000 lives in the United States.

The vaccine guidelines carry special significance: By refusing to allow the Food and Drug Administration to release them, the White House is undercutting the government’s effort to reassure the public that any vaccine will be safe and effective, health experts fear.

“The public must have full faith in the scientific process and the rigor of F.D.A.’s regulatory oversight if we are to end the pandemic,” the biotech industry’s trade association pleaded on Thursday, in a letter to President Trump’s health secretary, Alex M. Azar II, asking for the release of the guidelines.

The Food and Drug Administration submitted the guidelines to the Office of Management and Budget for approval more than two weeks ago, but they stalled in the office of Mark Meadows, the White House chief of staff. Their approval is now seen as highly unlikely.

A main sticking point has been the recommendation that volunteers who have participated in vaccine clinical trials be followed for a median of two months after the final dose before any authorization is granted, according to a senior administration official and others familiar with the situation, who spoke on the condition of anonymity. Given where the clinical trials stand, that two-month follow-up period would all but preclude any emergency clearance before Election Day.

The conflict began almost as soon as the Food and Drug Administration submitted the guidelines to the White House budget office on Monday, Sept. 21. The next day, Dr. Stephen M. Hahn, the F.D.A. commissioner, briefed Mr. Azar on the matter.

The Food and Drug Administration’s new guidelines were intended to assure companies developing vaccines that they were being held to a common standard and to reassure the public. Polls suggest that Americans are increasingly wary about taking a coronavirus vaccine: A survey published last month by the Pew Research Center found that 51 percent of Americans would either probably or definitely take one, down from 72 percent in May.

Dr. Peter Marks, the F.D.A.’s top regulator for vaccines, said last week in an event organized by Friends of Cancer Research that the government had to be transparent about the standards it was using to evaluate experimental vaccines in order to build public trust. He and other health officials have stressed that the companies developing vaccines are already fully aware of the agency’s expectations for products seeking authorization for emergency use.

“What the commissioner is proposing to put out is public emergency use authorization guidance on a vaccine that would be consistent with letters already sent to the manufacturers,” Mr. Azar said. “The F.D.A. has already told the manufacturers what they’re going to look for.”

Some vaccine makers, including Johnson & Johnson, have publicly indicated that they will follow the agency’s recommendations, regardless of the White House’s actions.

At a recent meeting with F.D.A. staff members, Dr. Marks said the agency “may hear more noise in the press” about trouble with the guidance but added that the “goal isn’t to get into fights,” according to people familiar with his comments. He said at the Friends of Cancer Research event that there was no reason “to get all excited” because “we are going to have a transparent advisory committee meeting for each and every emergency use authorization that comes through.”