WASHINGTON » Citing a potential threat to public health, the Food and Drug Administration moved today toward phasing out the use of some antibiotics in animals processed for meat.

Many cattle, hog and poultry producers give their animals antibiotics regularly to ensure that the animals are healthy and to facilitate the production process. Now, the agency has announced that it will ask pharmaceutical companies to voluntarily stop labeling drugs important for treating human infection as acceptable for those uses in animal production.

If the companies sign on, use of those antibiotics to promote growth in animals would be illegal and prescriptions would be required to use the drugs for animal illnesses.

The FDA is hoping to limit antibiotic resistant diseases in humans by decreasing the use of the drugs in animals. Exposure to antibiotics leads germs that survive stronger, so that they could withstand the drug the next time it is used.

Antibiotic resistance is a growing problem, and in September the Centers for Disease Control and Prevention released sobering estimates that more than 23,000 people a year are dying from drug-resistant infections.

The biggest risk is from germs spread in hospitals, and It’s not clear how much of the problem is related to the use of drugs in meat. But consumers have become increasingly concerned about the issue, and FDA has been debating how to address it for several years.

"We need to be selective about the drugs we use in animals and when we use them," said William Flynn of FDA’s Center for Veterinary Medicine. "Antimicrobial resistance may not be completely preventable, but we need to do what we can to slow it down."

The new guidance will give the companies three years to comply.

Michael Taylor, FDA’s deputy commissioner of foods, said he believes asking industry to make the changes is the fastest way to help phase the drugs out. If the FDA made the process mandatory, he said, the agency would have had to move forward with a complex regulatory process that could take years.

"We have high confidence based on dialogue with industry that this initiative will succeed," Taylor said.

Some advocates pushing to rid the animal food supply of antibiotics said the FDA did not go far enough. Democratic Rep. Louise Slaughter of New York, a microbiologist, said the FDA should have made the action mandatory. The guidance "falls woefully short of what is needed to address a public health crisis," she said.

Others said it was progress.

"We commend FDA for taking the first steps since 1977 to broadly reduce antibiotic overuse in livestock," said Laura Rogers of The Pew Charitable Trusts’ human health and industrial farming campaign. "There is more work to do, but this is a promising start, especially after decades of inaction."