The U.S. Food and Drug Administration, facing intensifying public pressure to fix the nationwide shortage of infant formula, says it is doing what it can to help the industry get more product to store shelves.

Federal regulators on Tuesday outlined steps the agency is taking to improve the supply of formula as the outcry from anxious parents and caregivers grows louder.

"We recognize that many consumers have been unable to access infant formula and critical medical foods they are accustomed to using and are frustrated by their inability to do so," FDA Commissioner Robert M. Califf said in a statement. "Ensuring the availability of safe, sole-source nutrition products like infant formula is of the utmost importance to the FDA."

The agency's powers are largely limited to streamlining bureaucratic processes. The formula shortage stems from the February recall of the widely used Similac brand, which strained an industry already lurching through supply chain issues.

In most food recalls, Americans can forgo consuming the products — such as romaine lettuce or flour — until the contamination risk passes. But formula is the only source of nutrition for many infants, especially those born prematurely.

Fewer than half of U.S. parents exclusively feed their babies breast milk up to the age of 3 months, according to the Centers for Disease Control and Prevention, meaning the majority of caregivers at least partly rely on infant formula.

Because of the nutritional importance of infant formula and the vulnerability of young babies, its production is a highly regulated industry with a few major manufacturers controlling most of the market.

Since the start of the recall, competitor brands have increased production, but it's not enough to fill the gap.

"Other infant formula manufacturers are meeting or exceeding capacity levels to meet current demand," the FDA said. "Notably, more infant formula was purchased in the month of April than in the month prior to the recall," possibly because of stockpiling.

Some retailers, including Minneapolis-based Target Corp., have started limiting how much formula can be bought at once, and the FDA is encouraging others to follow suit.

Similac maker Abbott Laboratories has not yet reopened its Sturgis, Mich., plant at the center of the recall. The company has increased formula production at other facilities and is importing formula from Europe.

Abbott is releasing some metabolic and specialty formulas — made at the Sturgis plant but are not subject to the recall — directly to consumers.

The FDA said it will expedite imports of previously approved formula and speed reviews for manufacturers looking to increase production. The agency will also use its "enforcement discretion" on minor label issues for otherwise-safe formula.

"Only facilities experienced in and already making essentially complete nutrition products are in the position to produce infant formula product that would not pose significant health risks to consumers," the FDA said. "The infant formula industry is already working to maximize their production to meet new demands."