The U.S. Food and Drug Administration (FDA) said Monday that it has finalized a new rule that aims to ensure that infant formulas are safe and support healthy growth in infants who consume them.

The final rule, which sets a date of Sept. 8 for manufacturer compliance, outlined good manufacturing practices specifically designed for infant formula, including required testing for the disease-causing bacteria Salmonella and Cronobacter.

The rule also requires manufacturers to demonstrate that the infant formulas they produce "support normal physical growth" and that their products be tested for nutrient content before they enter the market, and at the end of their shelf life.

"FDA sets high quality standards for the safety and nutritional quality of infant formulas during this critical time of development," Stephen Ostroff, FDA's acting chief scientist, said in a statement.

The final rule applies only to infant formulas intended for use by healthy infants without unusual medical or dietary problems, the FDA said.

The FDA said all formulas marketed in the United States must meet federal nutrient requirements, which are not changed by the new rule, although it does not approve infant formulas before they can be marketed.

If an infant formula presents a risk to human health, the manufacturer of the formula must conduct a recall, it said.

While breastfeeding is strongly recommended and many mothers hope to breastfeed their infants, most infants in the United States rely on infant formula for some portion of their nutrition.

According to the FDA, an estimated 1 million U.S. infants are fed formula from birth, and by the time they are three months old, about 2.7 million rely on formula for at least part of their nutrition.