WASHINGTON -- Concerned about drug-resistant bacteria, the Food and Drug Administration announced a new review procedure designed to curb the use of animal antibiotics that may pose a risk to human health.

The new policy is the FDA's biggest move so far to deal with an issue that has sparked world-wide debate. The agency will begin evaluating new drugs for livestock based on their possible impact on human health. If the effects are too strong, the FDA may refuse to approve it or restrict its use. The agency also plans to re-evaluate approved antibiotics using the same criteria. "It really is a new approach to the problem of antimicrobial resistance," said Mark McClellan, commissioner of the FDA.

Antibiotics have long been given to livestock solely to promote growth or in some cases to prevent, as opposed to cure, disease. Many countries, researchers and some in Congress have argued that the practice aggravates the problem of antibiotic-resistant bacteria and the practice should be halted.

The European Union has stopped the use of many animal antibiotics for growth promotion. McDonald's Corp. has also begun leaning on its meat suppliers to scale back their use of growth-promoting antibiotics.

The agency said that U.S. law forces it to look at products individually. "We think it's far better to look at the real risk ... instead of just disallowing a category of uses," said Lester Crawford, deputy FDA commissioner.

The FDA's new policy, which is termed a guidance rather than a formal new rule, will be integrated into the process of reviewing proposed new animal drugs. Depending on the results of its assessment, the FDA could put in place restrictions on how the animal drug should be administered, or reject an application if it deemed the risk to be too high. Possible restrictions could include monitoring by the agency after a drug is approved, and refusing to allow its use to treat conditions not specifically outlined on the drug's official label.

In its reviews, the agency will assess several different factors in deciding the risks to humans. One will be the likelihood that the drug could promote resistant bacteria in the animals that take it.

The second major factor is the likelihood that humans would ingest the resistant bacteria. The third would weigh the chances that the exposure of people to the bacteria would have an effect on human health.

The agency will also re-examine already approved drugs, and could restrict their use or possibly pull them from the market. The FDA could end up switching some drugs from over-the-counter status to prescription medicines, or narrow the uses the drugs can be used for.

Ron Phillips, a vice president at Animal Health Institute, which represents animal medicine makers, said the guidance will give companies "predictability about how their products will be reviewed."

The industry prefers the FDA's targeted-examination approach to simply disallowing broad categories of antibiotics. Cutting back antibiotic use in the latter manner can lead to higher rates of sickness in animals with no proven benefit to human health, Mr. Phillips says.

Write to Anna Wilde Mathews at anna.mathews@wsj.com